I guess it depends on the website. Forums generate a lot of page impressions and usually a low CTR because of the nature of the site.

Also, the reason forums and websites may get higher pageviews than they actually do is due to the adrotator, it actually generates it's own pageview when a banner loads. So my advice is, be careful when you buy or sell advertising space because you're probably only generating 1/2 of what the impressions say. Also, if you have a footer and header rotator on the same page then that would count as 3 pageviews.