That said, I've had a lot of these calls and fortunately not fallen for them once. The funny thing is that eTrade (I think) has a system where you can ask for a callback but then they'll go right into taking your information. When that happens, I followed the play book: I asked for a phone number that I could find on ETrade that I could add an extension for to get to this person. He gave it to me and everything along with some sort of quick access code I was supposed to use to get whomever I hit to pass me along.
Well, I did the whole thing and the person at the other end in the ETrade system that I dialed said "It's okay, I'll just take care of it, sir". I mean, at this point I just sucked it up and went through with the process since I figured I dialed the number from their website to get there and then the extension so surely it has to be legit, right?
But I just know someone is going to point out a way that I could have been scammed through this mechanism.