The term "Cheese" comes from the adjective "Cheesy". The not-so-subtle innuendo there is that a victory via so-called "cheese" did not come from the players own skill, but was merely because the loser was unprepared for the "cheesy" tactics that lead to their loss.
What qualifies as "cheese" will undoubtedly vary from player to player, but generally the term refers to exploiting system mechanics in a way unanticipated by your opponent, or otherwise not balanced around.
Many people dislike cheese because it is hard to predict and counter if you are not prepared for it.
Several Examples:
- Thor Rush -- build a factory near your opponent, attack with Thor + repair SCV's around 7 minute mark.
- Photon-Cannon Push -- rushing a forge and placing photon cannons around your opponents base.
- Banshee / Void Ray rush vs. Zerg -- takes adavantage of the fact that Zerg has little viable anti-air at T1 other than mass queens.
- Proxy Rush -- Building a unit production facility much closer to your opponents base than your own so that you can reinforce your troops faster.
- Worker Rush -- in 2v2 (or more), making no units, and instead attacking another player with your workers alone.
It's also a question of cost and predictability.
MMOs are relatively low stakes, and tolerant of downtime (particularly with region specific downtime windows). Google gets heavy traffic 24/7, but a MMO like WOW will fluctuate massively throughout the week. The impact of brining down servers during those valleys of usage is disproportionately lower than it is in other businesses with more regular activity periods.
By implementing regularly scheduled maintenance windows they also gain predictability. I would hazard a guess that, if they wanted to, 90+% of what happens in regular maintenance could be moved concurrently. They might still have some downtime windows occasionally for big things (replacing core network infrastructure, upgrading major patches, etc).
However there are some trade offs. They would still need occasional maintenance windows (when do you schedule them? Would people be more upset by occasional random maintenance windows than a predictable, consistent one?) Would the systems be much more complex? Would it be much more costly to add new features, innovate and maintain?
Also think about the nature of the servers in an MMO vs other online games like Starcraft 2. In Starcraft 2 the games are pretty much happening between two players. The servers have to coordinate the games, but there's a lot more fault tolerance and less need for global synchronization. Starcraft seems much more like a tradiontal website architecture than WOW, which is a more unified system. In WOW everyone needs to be in instant lockstep.
Basically the short answer is that there are dozens of reasons that a maintenance window can be used for, and the reasons for not doing one with an MMO specifically are pretty slim. The whole MMO software system can be much simpler and more predictable if they schedule and use a regular maintenance window, giving you a better game cheaper.
Best Answer
The name Masamune doesn't reference an actual sword, but a legendary sword smith called Gorō Nyūdō Masamune. (Altough, his name is also attached to his swords, like Honjo Masamune, Fudo Masamune, Hōchō Masamune and Kotegiri Masamune.) And for this to make sense, you need to understand that Masamune isn't regarded only a great swordsmith, but the great swordsmith. You can read more from the linked Wikipedia-article.
The same hold true for his pupil, Senji Muramasa, whose name you've no doubt also heard in similar contexts. (Pupil as supposed by legends, actually, as some sources state that they didn't even live at the same time periods.)
Masamune's and Muramasa's names are widely used in Japanese popular culture to refer to either legendary swordsmiths or swords. So much so, that this has became a sort of cultural meme.
Something I see often is western game developers, who most likely know the names only through games, using these to refer to only swords, as opposed to people.
For more on the cultural side of the two names, mostly their use on swords, see their TV Tropes article (beware of getting lost on that site).