This is a horrible idea. That turns users away from a site extremely fast. If they Google something and one of the results happen to be LG. They click it and they are greeted with a "you must register" screen without letting them see the content. That usually just turns people off and they go to the next search result.

@Temptii it is built into vBulletin, all you have to do is click a radio button and it's done.