LetsForum.com allows users to display their AdSense ads every time they post for free! The way it works is:
You provide your AdSense ID number and every time you post they use your AdSense ID for AdSense ads that you see on top of each thread! So imagine if you have 200 posts and 2000 people see those posts every day that will generate you a lot of income!
By the way you get paid by Google AdSense and not by LetsForum.com