They pulled the same thing on me despite completing about a half dozen 10 BTC purchases over the course of the last month.  They waited a week to cancel my supposedly "high risk" transaction, but they have not yet canceled my other pending transactions or closed my account.  It seems like an immediate account freeze would be the first course of action if any sort of fraud was truly suspected.

Overall, this is a big disappointment because it seemed like Coinbase was finally the first professional service for buying and selling coins.  Unfortunately, it looks like it's still amateur hour in Bitcoin land -- as usual.