Although I understand what you mean, in these circumstances I find that their free bet promotion does not produce the desired outcome. One could even say quite the opposite. I would personally rather opt for some form of bitcointalk-exclusive promotion. It is much easier to prevent abuse if you limit the promotion to forum accounts only.
That's the problem always, free money will always attract scammers and players who want to abuse the system. A bitcointalk exclusive promotion (and only from member rank or higher) would indeed be more interesting as the amount of abusers would be a lot lower. I still like casinos that give free bets as it is handy to test out a new site without spending any money.