For me, it is the good content. On other sites such as reddit, there is a whole lot of content, but not as high quality as the content on Snapzu. Also, the downvote system encourages users to continue to post high quality content. On reddit, the consequences for getting downvoted are low. Here, your total reputation lowers.

Another benefit of the downvote system is that people will think, and usually respond, before downvoting. On reddit, users reputation could be completely demolished with one comment.

I also enjoy the lack of a hivemind, and I enjoy the acceptance of all opinions.

So far, my Snapzu experience has been a good one.