It seems to me that CPA networks would obviously be one of the best means of building highly-targeted lists outside the internet marketing niche. I did a test run on a big name network with $100 and a $10 daily limited. I still have money in the account and got 9 leads in the dating niche. This was done just to see what would happen. I did no real work. Just think what would happen if I pursued it aggressively.