Interesting observation. Actually, I think most of the devs are against filtering SD, too. There is just one very vocal one against it. As far as I can tell, all of the long-time devs oppose any filtering, since SD is working within the limitations of the Bitcoin protocol as it is defined. Please correct me if I'm wrong. But I agree with you that SD could try to find some ways to reduce the quantity of spam. One simple but drastic solution would be to run their own block chain and use it as poker chips that players could easily buy with Bitcoins (once you're in the virtual currency system, exchanging currencies is trivial).