I reckon Mike's Right Dynamite... could be good but make it simpler... rather than trying to offer the deal for every site in your database, maybe make a smaller paying members area that focusses on a few featured sites letting you send more volume to each one.
One other issue I see when negotiating a deal with sponsors is that a surfer who joins several paysites per month would be worth less in profit per signup than average imho.. and the programs that pay the most often seem to use generic members areas too so if you try selling you're visitors to them multiple times it will become a chargeback problem.
Here is an idea you are free to take if you like (if you can make it workable) I spoke to a rep from a big company recently about a similar concept to yours but.. my paying members would be given short free trial access to a paysite member areas. The paysite owner would need to setup your site as an allowed referer to the member area but that should be all that is needed on their part... then you provide your members with a short time based session to access the area.. I was thinking 15-30 minutes.. at the end of that time the surfer is transported to a page prompting them to continue to the signup form to continue enjoying whatever content they were in the middle of when the session expired.
The rep threw up a few objections like the profitabilty issue I mentioned above.. But in particular, that this type of site would attract a lot of content leach program users... that would log into each site and use an offline browser program to suck all the content.. and never join anything.
If you can address the profitabilty part, the security, think of a way to limit the content leach problem and create enough volume, minimum 100 signups a day would be my thinking, then I reckon it could be a real winner
