People said it was fake last time, and we saw a blog post just like this 2 days before the sell-off.
If anything, that increases the odds that this one is fake. Both Bitcoin users in general and anyone that wants to fake a security scare about Tradehill have the Mt Gox compromise on their minds, so a fake is likely to take the same form as the real Mt Gox compromise. It's unlikely that a genuine hack would happen the exact same way as the last one, right down to the message offering up account details for sale.