I just bought one of the XXX sites from Tibet230.  The login seems to be working fine.  Even if this person was a scammer, the invite was only $10 for this particular site..

Side tip: I wouldn't buy an invite where they just give you the login and password with no e-mail (e.g. buffered account).  I lost access to one recently, and I couldn't reset the password, or find out what's going on.  I think it's better to start new.