Forum Moderators: skibum
I wouldn't do a CPM program unless the payout was $20/cpm or more. Additionally, it's hard for a visitor to tell if the third party pop is spyware or generated by your site.
If you plan on repeat traffic it's a bad idea. The payout also kind of bites. I would recommend looking into targetted affiliate programs or if all else fails google adsense.
$0.50 CPM? I wouldn't even do that for a regular banner.