You all know what I am talking about. The page loads and boom... right smack in the middle your webpage a pop-up/over is displayed offering shitty freebies or periodic spam. Even worse is when the pop-up/over timer is set to show after a certain number of page views. You are not clever, you are most likely killing page views, time on site and jacking up your bounce rates. For what? Fake email addressees?
I understand having people give you their email address is a great feeling but the whole pop-up/over thing is a poor user experience. Have you not learned anything from the past? Browser pop-ups sucked and pop-up/over plugins are even more annoying. If you need to have one, move it and don't obstruct my view. Any developer who feels the need to show a pop-up/over is almost as bad as the publishers who require users to 'like' to view a video.
There are two ways to do something. The first one is with taste. The second one is a pop-up/over.
You decide.