It appears they may be using unconfirmed outputs in the transactions they generate to send you your bitcoins. That's just too much risk for me to be allowing them to pull money from my bank account. Until they resolve this issue, I wouldn't trust them enough to receive any transactions from them.  By the time they've sent you the bad transaction, they've already got the money from your bank account.  How do you straighten that out?

EDIT: Apparently coinbase is fixing the bug.  If I get confirmation that the bug is fixed, I'll delete this message.