^ Not every one has ad block or dislikes ads, especially when they're highly relevant to the subject of the site.
According to this site http://websitesoutlook.com/forum.bitcoin.org
, and I don't know how credible these numbers are, the forum has 216,284 page views a day. That means it could generate $200-300 in ad revenues a day.
The question would be, how would the ads be paid for, with dollars via an established ad network like Adwords, or with bitcoins. If with bitcoins, there is a bitcoin ad bidding network here:http://www.operationfabulous.com/
Or the site could solicit bids and place the ads manually. That would be more work though, but it would allow for the ads to be screened for the quality of the product/service they're advertising.