battle.net choose your quick match based on match making rate (MMR) which is remain hidden by the server. Do some reading here. it'll help

http://wiki.teamliquid.net/starcraft2/Battle.net_Leagues

here are more detail explaining about MMR

http://www.teamliquid.net/forum/viewmessag...topic_id=118212

This post has been edited by potion: Oct 9 2010, 08:31 PM