When I go to join a multiplayer game in StarCraft 2, sometimes the game client says it is downloading a few items before it enters the queue. This notice appears at the top center of the screen, and is soon replaced by the the "looking for players" message and then the "players found" message.
What is it downloading? Presumably I already have all the game content, and also presumably it can't fetch data on my opponents (such as their avatars) until it has decided who to match me with, which can be minutes later. Blizzard isn't issuing micro-patches this way, are they?
Edit: After the recent patch, these downloads took even more time. I'd love to know what's being downloaded, so I'm adding a bounty.
Best Answer
I noticed earlier today that as of 1.1, the Blizzard maps were updated from v0.1 to v1.0. (Agria Valley is currently at v1.2.) Also, in the SC2 Editor, some Blizzard maps are showing up as not downloaded:
I haven't played 3v3 since pre-1.1, so all the updated 3v3 maps are still marked as Not Downloaded.
This supports Mag Roader's theory that the downloads consist of map data.
So, here's what I think it is: When you join the matchmaking queue, the game asks Battle.net for a list of maps you might about to be playing on. If you have the latest versions of all the maps, this will probably only take a second.
If any maps are out of date, however, the game will update them. This will take a few seconds for each map since they're around a megabyte each.
This system would let Blizzard publish updated versions of maps, or add new ones to matchmaking, between actual patches.