I don't understand you people. We have our exchange operating for several months, with a team of 6 people working on the software. TradeHill, Bitcoin7, bitomat, CampBX are all much more professional than mtgox too...
And yet mtgox with super shoddy security (it's not even funny), many problems and people still stick with them?
Mt Gox is where all the volume is, so everyone trades there. I think someone on the Something Awful thread had a particuarly pithy way of putting this, but I can't be bothered finding the comment.