I think the recent MtGox debacle will at least open up the competition considerably. Ideally for consumers several exchanges take a piece (but not a landgrab) of the market.
You're quite right. BitCoinMarket.com would've been the first competitor had it been non-invite as it is now, which is why TradeHill.com has seen a surge in users registering.
The problem is, people aren't realizing that other exchanges may not be secure! MtGox mentioned what kind of password hashing they were using and to which one they've switched to now. Also, they did emphasize on the fact that their website wasn't breached.