I saw this kind of a system being used in the Paradox Interactive forums where you can only access the sub-forums of games by being a legitimate user of that game ie. they have a page in your forum profile where you can enter a CD-key for each game they publish and by entering that key and it being verified as a legal copy of the game, you get access to that games forums. I find this as an excellent idea to give legitimate users a feeling that the company actually cares about providing service to their legitimate customers.
I believe that a similar system could be adapted on these forums too if not limiting all game sub-forums to legit users but sections like for example with the A2/OA forums you could have "News", "General" and "Questions and answers" open to all users of the forum and "Suggestions", "Troubleshooting", "Beta patch testing" and the rest only open for legitimate users. And even if you would not completely close the forums from others, make it so that only legit users could post there and others would have only read access. I believe this would cut down posts from people who want to just troll and don't even own the game(s), people posting about issues that are related to pirated copies etc.
Now I understand that this is by no means an easy or quick system to build BUT since all the games seem to use a cd-key system anyhow this would provide an excellent "extra layer" for the use of these keys and as a paying customer would make me feel more appreciated too when you "gift" me with access to the information that basically would be needed only by people who own the games. On the same note although maybe going a bit too complicated, unifying the forum accounts to BIKI accounts and limiting the BIKI access to legal users only would be an excellent addition of this system.
The only thing I see a problem here is the Arma 2: Free users. I don't know how the system works in that for players (do they get cd-keys?) but then again A2: F is in itself limited from most of the stuff that would be limited in the forums anyhow like mods, single player campaigns etc.
To end I'd like to point out that I do not see this as trying to control or limit the access to information about the game(s) but rather as a service for paying customers as a thank you for buying the game(s).
Your thoughts about a system like this?