To be honest, I don't think you have to worry about someone joining the site, posting 50 times, winning a psp and then leaving. Chances are pretty slim that someone with those intentions are going to make 50 worthwhile posts in a month. What it is going to do is bring in a lot of people (myself included) who don't look at the topics every day who might actually have valid input. Sure, I haven't been here incredibly long, and probably have a pretty low post count, but I'd like to think that when I do get around to posting something, it's useful.
I think the admin is trying to get people like me who have some decent insight into topics to actually come around and post more often. Develop it into a habit .
Besides, all these posts are driving up the server costs... I don't think he plans on rewarding people who uselessly waste his money.
-D