Adding Pop-Unders/Exit Popups to a LP

I figured I'd post this in this section b/c it can be applied to a variety of sections BH/WH/etc. When do you think it is appropriate to put pop-unders/exit pop-ups on a landing page?

I'm doing adult affiliate stuff now and I'm wondering if it would increase conversion at all. I'm not experience with actually using popups or popunders so I was wondering if any of you had some insight to share whether you feel it feeds your income or takes away.