I have a Forum which is a pretty good niche (the only dedicated forum about the 2nd most popular mp3 player brand) And its been up for about 2 months, and has about 1800 posts and 175 users. Sure the forum is building well.
The question is that i want to do an experiment. I just want to see what happens if I made the forums private, meaning only registered users can read it. I was thinking that sure, it may turn away a good portion of visitors, but in reality, only about 1% of visitors register and post. If people are looking for something (like a theme for the player) they are likely to register just to get it. And if they logged in, it is more likely they will post.

I know that this will probably make me lose a few good number of "guests", but if I do this, I might get a few portion of new users. I am only intending to do this is a period of a couple of days.

Has anybody had any experience with this? was it a bad mistake? Is it a good little tactic? Opinions please !