Blizzard is currently in the process of linking up play regions for the RTS to bring more players together.
An annoying problem with most match-up systems is the segregation of player regions, especially for games such as StarCraft 2. Blizzard is taking steps now to links up some of those regions which will increase the player pool for each region.
Blizzard is linking the European and Russian StarCraft 2 communities together, North America and Latin America and Korea with Taiwan.
The reason this is being done is to help the automated match-up system match players quicker which means less waiting around for a game. It will also give access to a broader range of custom map games.
No date has been set as to when the system will be updated to link the regions.