A quote from another major site regarding this is..

"I have reviewed the Google Adsense Policies a few times now and I haven't found anything that disallows this system to run."

There are a few sites that run this system.
Do not though encourage visitors to "click" you will get banned.
I would also monitor very closley.

Maxseo,
If you find the hack to impliment that, let me know, I want to start similar scheme for this forum so that people who start a post can get adsens ads placed under such posts.

This is a good way of spreading some ju ju, but be careful who you allow. If you get some clown clicking on ads you will get banned without doubt. Dp is a profit sharing forum and that runs well. (although I do not ad any adsense code there as I worry about vindictiveness)

That is a very good point OWG, you just need some silly fraudster to mess up the program, I think I need to give this careful though before proceeding.

I came to the conclusion that it is not worth it, too many risks. I think enough of the attraction is that my directory is free
..

thanks for sharing that info, I think I will put it on ice for now as well

I've not sure if I've missed the point, but can't you set it up so that people get a share of the total revenue based on the number of uniques going to that page?

Yes Rob,
But the problem is that not everyone is honest, some people will commit click fraud and you will be help responsible as the organiser of the scheme.

Well, DP has been offering this feature for a while now and they have not been banned. So I'll say it's kosher to go for it. Just make sure that you know not to show the adsense ads from a user to himself. You can prevent this by looking at finding out when a user is logged in or when you detect his IP address.