I removed the post before you posted, so sorry for that. I don't know, I see it as a method to convert lurkers to members, but it might put off other users, like you mentioned. Although I think people who lurk will eventually register at some point, why not lend them some help. People who read one or two posts from your forum would not be put of as they would not run into the restriction, but would also have less chance to convert to a registered user.
As an Internet user myself, 95% of the time when a website has a huge pop-up to force me to register results in me leaving the website and not returning.
As an Internet user myself, 95% of the time when a website has a huge pop-up to force me to register results in me leaving the website and not returning.