They can be an annoyance for site visitors, but provide a nice little extra income for the publisher. If you've got a high traffic site set them to display once per IP per day and watch the cash roll in.
Dont use a full page ads, they're really annoying and I wouldnt like a site that used it. Ofcourse if your site is something that people will come back to and actually put up with the ads (like a porn site) then its ok.
I personally recommend them but do not overdo it. As CountryBoy stated, display them once per day, per IP (unique visit) so that visitors will not be annoyed too much and see the ads each time they visit your site. Annoyance can actually lead to losing visitors/members depending on your niche.
the full page ads is a excelent option for publishers to make a quick buck but on the other hand if you set it too frequentaly you can easialy loose visitors
these days most of the high end forums seem to be using them..i myself have used them...they generate a lot of cash for the publisher but yes they are quite annonying for the visitor..
Well I would've put a longer time if possible, but the longest period of time they have is 24 hours. I saw clicksor just recently added this feature too. (full page ads)...
When I started with them they were good but now after 2 months revnue has fallen to more than 70% for same number of pageviews. But I still love them. Good option with adsense
I would use them with adsense but my adsense account was disabled because I was considered a risk to advertisers. I think that's because I don't have a large site with lots of content.
I think there worth it if you have content that is not easily found elsewhere, as you users will have "to put up and shut up", if you are working in a very compettive niche however avoid them! - your visitors will just flood to your competitors.