An affiliate manager of mine pointed me to a survey offer and told me that one of the best affiliates promoting it is using incentivized marketing on Facebook. He is using ingame advertising on games like Farmville to get visitors. Each visit is incentivized because the surfer is getting rewarded with credits when they click his offer. I don't know whether it's ingame credits, Facebook credits or something else. The affiliate is still getting the normal payout, because he's not incentivizing the lead itself, but the click. His click to lead ratio is still quite high, probably because most visitors think they have to complete the lead as well. Or maybe they're already in a winning or 'getting something for free' mindset 
Now, I'm not really up to speed with this part of marketing on Facebook (ingame advertising). His volume is quite high (> 1000 leads/month for a small European country), so I think it must be through some kind of advertising network. It also sounds like he can select the countries he wants to target.
Does anyone know more about this kind of marketing? Where can you do it?
yes
http://www.adknowledge.com/
they have many options.....but its limited what you can run....as it still needs to meet fb terms per se....500 min deposit...also they work direct with alot of advertisers already...so finding something that will "work" can be tough....(was my experience direct linking)...
go here.... http://developers.facebook.com/adproviders/
this is a list of approved 3rd party adnetworks on facebook
contact them and ask....