I've always been a bit puzzled about the way Paradox handles this. It's not necessarily a bad idea, but it's fairly off-turning if you have a question about a game and can't post it because you don't have the game. There are plenty of non-constructive posts over there, too, so this approach doesn't guarantee more mature discussion. It almost certainly does lead to more sales, though!
I believe that a community -- any community -- needs to be able to handle disagreements and minority opinions, and even stupidity, if it wants to really grow, thrive and become strong. In a forum context, the problem is often that the established users give attention to trolls (whether actual or perceived). Attention is a reward and if it was less freely given to people who don't contribute to the (your) community, the ripples they cause would be smaller or non-existent. It's just not fun if your attempts to cause friction don't get a response.
(I'm not referring to people who have valid concerns and voice them constructively. A community needs these people and there should not be an entry fee. Plus, there are also some "game owners" who flame everyone whose view differs from theirs.)
