I just took a look at this and I like the concept. I kind of wonder if my game falls in line with their model though. Users would essentially buy tokens on my app and then use them which could result in a reward. So they are buying a service for a small fee.

It seems like social gold is more focusing on assisting a community or a large virtual world. I don't have that, but I do see they also identify it as useful for services. I guess I need to look more into it. I think what I will do is release my beta to HN and ask what they think I should go with. Ultimately some form of payment will be required, but I am not sure if I am approaching it in the best way.