The problem with having to moderate user's first posts is that a lot of times it turns the users off and they never return. We want to be as user friendly as possible, not cause a huge burden for moderators and also make it so that users can get their posts responded to ASAP rather than having to wait for mod approval. I think that we do a decent job removing spam for the most part, especially when people report the spam. Always feel free to hit the little report button if you see any spam messages.