My guess is they use the same tracking tools to target advertising. I don't like being targeted for anything, even if it is a product or business I like. However, it could be similar to asking to be on an e-mail list for a specific vendor. I've done that with a few. Perhaps they allow your own parameters for targeting.
Ex from front page -
Your Community The Community is the forum where you can connect with like-minded people near you. Join groups, feel connected and rally behind the causes you care about all in a censor-free environment.
- Join Groups...There is a block list of different 'groups' near the bottom of the front page.
I have not signed up, so I don't know anymore than what is on their front page. http://www.publicsq.com/