Do you want to know how someone can lose or how he did lose?
Bly lost because he played very poorly: he did not build enough drones.
Take a moment to let that sink in, because its a very very big mistake and its the difference between a good Zerg player (like Fruit Seller) and a bad Zerg player (like Bly).
Instead of backing off after taking the Terran Natural, he continued to press in. He sends wave after wave of a consistently sized army. He does this because he's not building more drones so he cannot afford a larger army. By comparison Tarson's army gets larger and larger after every wave. He's able to continue to accumulate units because he has a fairly healthy economy. This is due in part to MULEs, but largely because Tarson built enough SCVs. Even after losing his Expo he still has as many workers as Bly does. Think about that for a second. He lose an entire base and all his workers in it and he still has more workers than his opponent.
This game could have easily been one that was featured on Day 9's Newbie Tuesday
I could point out a dozen mistakes that Bly made, but none of them matter nearly as much as his poor drone usage. Because of his lack of drones, his assault becomes almost an all in. So in response to your question How is it possible Zerg with biggest advantage can still loose to Terran? Bly didn't have a big advantage. He sacrificed his economy on a gamble and it didn't pay off.
But let's imagine another universe, where Tarson wasn't playing Bly but was playing against a better Zerg like IdrA; and let's assume IdrA made the same early push.
Now IdrA is sitting on 2 bases to Tarson's 1, but they have equal workers. So instead of continually pressing his advantage, IdrA decides to play like he always does: Macro. He sits back and takes a third base and powers drones. Tarson retakes his natural and now he's down 2 to 3 bases. Not a big advantage for IdrA, but remember a Zerg can make drones faster than a Terran, so it takes Tarson longer to saturate that 1 base than it does for IdrA to saturate his 3. Now IdrA has a huge economy and he goes Roach/Hydra (or these days he's favoring Muta/ling, but pretend).
Imagine that battle for a second... or don't, because it actually happened. IdrA knocked out Tarson in IEM, exactly like I described.
The smartest thing you can do in Starcraft if you are ahead is to get more ahead. Anyone who played seriously in Broodwars knows this because if you pressed like Bly did, you got destroyed 100% of the time. Now Starcraft 2 is still new so a lot of people feel like they can do crazy 2 base play, but if you look at the high end GSL matches you see less of that and more of people trying to get more ahead.
You also mentioned a quote talking about Marauders vs Banelings. Now I don't think that the relationship between these two units had anything to do with this loss, but let's talk about them for a second.
Banelings are a highly specialized unit. Their role is to act as Zerg splash damage on light units. By comparison the Marauder is a more generalized unit, designed to act as a Meat shield (much the way the Roach acts for the Zerg). So it makes sense that a Baneling doesn't function well against Marauders (as that's not their role), and it also makes sense that Marauders do a good job of preventing Banelings from striking other units (as that's their role).
I would hesitate to say that a unit is broken because its functioning in its role and another unit isn't functioning in something outside its role. But let's say you want a way to deal with MMM balls. Instead of sending it waves of Banelings on their own. Consider mixing in more Zerglings (Bly actually does this to large effect). Now let's vary our composition based on their unit mix. More Marines? More Banelings. More Marauders? More Zerglings. Can't find a good place to engage? Burrow/Drops/Fungal Growth/Wait and Flank.
Here is the key thing, none of this is any assessment of Banelings against Terran, but rather an assessment of the tactics used.
Best Answer
For a player that is in the gold league, your initial build orders seems very solid, at least a lot better than other gold zergs that I have met before.
One fundamental rule that you have to remember about ZvZ is this: Anything can happen at any point of the game. ZvZ is the most volatile matchup out of any other possible ones largely because of Zerg's capability of producing a massive amount of units quickly. For other matchups, given enough training, you are able to narrow down or at least get an intuitive feel on when your opponent may attack you. In other words, there are a definitive set of "timings" for the attacks you can expect but this simply isn't the case for ZvZ.
Consider this: For ZvT, even if you didn't know 100% of what your opponent is doing, you have the option to be a little bit greedy and pump out drones as long as you don't over do it, because it actually takes a while for the terran army to march all the way down to your base (This is why creep spread is crucial in ZvT). For ZvP, there are only a limited set of potential timing attacks that is employable by the Protoss, such as 6 gate, blink stalkers or the dreaded parting style all in. For ZvZ, none of the above I talked about applies, because it takes seconds for the Zergling army to arrive to your doorstep and they are very easy to produce.
Now I will apply the above principle to the replays you have uploaded and talk about the specifics:
1.
The opener you scouted your opponent is the infamous aggressive 14/14 and happens to be my staple build order. Since you opened with a pool first then hatch, there should've been only one thing that crossed your mind: He will attack me in the vicinity.
And your response? You kept droning... and you waited until the last moment to start producing Zerglings and a spine crawler.
And this is basically what ended up happening:
You might be thinking, "But hey, what if he didn't attack me and instead decided to heavily drone?". Well, there is an important lesson to be learned here. You need to consider both of the worst case scenarios that could happen if your opponent had put the aggression on you vs if he didn't decide to be aggressive and start droning himself.
Really, it comes down to a simple logic like that. Now tell me, being a pragmatic and a logical player, which one of those cases sound better to you? In fact, it is more likely that you would be slightly ahead in drone count even if your opponent had started to drone because you had your hatchery done first.
But what if you screwed up somehow and overcommitted with the zerglings? No problem, put some pressure on your opponent, prevent him from droning and in the process, start making drones for yourself. This process goes back and forth in this volatile matchup.
Other problems I wanted to address are your mechanics and map awareness. You state that you blocked the ramp with the queens. In fact, you didn't properly block the ramp because you sent your queen from the main down to the ramp way too late.
You built a baneling nest, which is a good response but during the aggression, you didn't realize the building was completed and didn't accordingly start to produce banelings.
In fact, because your opponent carried out the attack somewhat badly, you could've easily defended that attack at the moment the enemy lings left his base and be substantially ahead in the game.
Since I happened to have some Korean DNA embedded in my body, which means I get a racial passive bonus in ability to play Starcraft well, I am luckily able to demonstrate this point. Blizzard recently implemented a very nice replay feature which lets other players take over in any desired point of the game. I've asked my brother, who is a top master player to take over as your friend.
Now that I've extensively covered one replay, it gets easier to answer the remainder ones:
2.
This one is easy. You were so severely behind when you cancelled your first hatchery that it is safe to say you practically lost the game at the moment the hatch was cancelled. The thing is, that hatchery did not need to be cancelled at all. You could've let your hatchery tank a bit and buy more than enough time to produce 2-3 sets of lings to defend that light aggression (more like scouting in my eyes).
3.
Recall the most important fundamental rule I have reiterated over and over: Anything can happen in ZvZ at any given point of time. Ever wonder why professional players would make few banelings and a spine crawler at his natural when both players are in fact, droning? It's because of this very possibility from being overrun by the zerglings and losing the game.
The banelings play a critical part to buy you enough time to produce more lings and spines to defend yourself. And there's no reason that you couldn't because as you said, you were floating on a lot of minerals which is another sign that you need to improve your mechanics.
4.
Same issue as #1. You were droning hard when you should've been making zerglings and banelings.
Regarding your thought of a hidden expansion, you should've completely ruled this possibility out when you scouted his 14/14 build. It is illogical to build a proxy expo in the early game where each other can be scouted very easily. Unless if the sun rises from the rest and the moon turns red.
Miscellaneous
Your general understanding of the game seems to surpass that of a typical gold league. If you consistently practice your mechanics and try to logically deduce why your opponent might do A or B, then you should be able to hit platinum or diamond league asap.
Additionally, please read this matchup guide posted from Teamliquid. It should give you an insight of how ZvZ works generally.
http://www.teamliquid.net/forum/viewmessage.php?topic_id=401063#2.0