A colleague of mine recently received complaints from friends claiming she'd posted comments on their MySpace pages sharing a bogus coupon that was really a phishing attack. The problem was, she never posted the comments.
Now, I need to point out that my colleague is about as technical as it gets, so it was unlikely that she'd used a weak password or let her computer get trojaned. In fact, her MySpace account showed that no messages had been sent from it. Nonetheless, the people she heard from were part of her MySpace friend list and the messages came from MySpace.
It's very unclear how this could have been perpetrated other than MySpace, itself, getting hacked. Regardless, this kind of phishing may be the most insidious kind to ever exist and definitely something for all of us to keep an eye out for.