I don't think the excuse should by, "they do it and so can we" works.
Look at the site who don't do it and look where your traffic goes. I have never ever been to a mainstream site that poped up so many I hade to close my browsers, maybe they do exist just not found any. 1 pop up to suggest something else is fine. Some sites in this business just went over the top.
How much do surfers mind? They use pop up blockers that we write scripts to get around.
