My site (and thus also forum) is down right now 'till next month, intentionally, but I will speak as though it is not down.
I would think a web site in it's entirety would gain you more money than just a section of a site such as a forum.
I don't make any money through any of my site. I try to get a little money through Google ads (ads is spelled a-d-s, not a-d-d-s, add
) on my web site and forum, and a paypal donation button on my web site, but I haven't actually recieved anything. I just don't get enough visitors. And I really don't like ads that much so I wouldn't put anything on my web site worse than Google's text ads, because everyone knows how annoying image ads and flash ads are.. People always avoid the sites that use ads that distract viewers from the actual page content by moving or flashing or whatever.