Advertisers control content, boycotts work.
ads also allow for better tracking of posters (which is already happening in many pages when users post simple 1x1 pixel tags)
actually, a quick check shows each page has a google analytic tag hooked to acct UA-2288668-1
this allows google (and the NSA) to track every user to the site and where they are posting from
this would also allow them to get browsing habits from other sites as well
Hardly ever and, well, hardly ever. At any rate, it's not a valid argument for this situation.