I dont know about you, but when i visit a forum, i usualy lurk for a week or more. I see if i will fit into the community, to see if the standards are upto my own standards... If i recive a popup for every page i visit there, theres no way your going to get me to register! If you do that to guests, how do i know you wont exploit members down the line? I think one pop-up per day is enough.