Well, the effort the affiliate puts in is in bringing that traffic to their own site. The surfer may have accidentally clicked your banner, but the affiliate spends a lot of effort building pages, and then promoting them. Surfers get to an affiliate's page by link exchanges we made and SEO efforts.

Is a 50/50 revshare fair to both sides? Well, if you had one content producer and one affiliate only, I would say the content producer should get more, because he would have more expenses. But, you have one content producer with hundreds, or thousands of affiliates, so the sunk cost involved in producing the site is divided into thousands of those marketing channels...

I sometimes wonder about the fairness of it all, going both ways. I have had so many sponsors that don't convert for me. I spend a lot of time in sending some sponsors literally tens of thousands of clicks without a single sale. Is that fair to me? I brand their website, and who knows, maybe the surfer just cleared their cookies and got back the next day and signed up, for all I know. Wouldn't it have been more fair for us to get paid per click? Do an adwords sort of system and pay 30 cents per click (with link text controlled by you, so no blind links)? I surely would have made a lot more out of it that way. Most of my income is from adsense (mainstream sites) and I sometimes think about how unfair the whole adult affiliate model is where I get much less for my traffic then I do on mainstream. Effective CPM on mainstream is usually $2-$6. Effective CPM on adult in measured in a few cents. The work to bring in the traffic is similar...

Just some thoughts and ramblings from the affiliate side of things. And btw, I would much rather get only 40%, heck, even 30%, from sponsors that convert and retain. Right now I am seeing ratios of 1:3000 or so, with good search engine traffic (no TGP), with some sponsors. So, no, at these ratios, I think I deserve a fair share of the cake, or it simply wouldn't be worth my time at all (is borderline as it is now).

Last, but not least. Some paysites don't have affiliate systems, so I hear. I also hear that when they want to grow their audience significantly, many do go the affiliate route... I guess it makes business sense, or it wouldn't have happened