What probably happened is this: The seller might have been legit, but some of his "friends" had account info and upon learning of sale, figured hey, free acount to abuse..
If you buy an account, always, always get the owners address/phone and actually talk to them first. You chances of being ripped off decrease dramatically then.
That said I have gotten lucky twice and traded plat for accounts that still work without having owners contact info.
Problem is that for those accounts I didn't bother changing Secret Question when I still had a chance. Now there is basically no way of finding out.
For some other accounts I was able to just track down first owner and find out answer to SQ.
I'd seriously pay $50 to anyone who can provide me with a working method for changing SQ(and thus pw) or just pw.