I've always wondered this, but was a little scared to ask. Perhaps now I can. 
Will these forums here ever allow search engines to visit? If I'm reading the robots.txt correctly, the major SEs will not visit:
User-agent: *
Disallow: /forum/ # This is an infinite virtual URL space
To my mind there are many reasons why allowing search engines to spider this content would be good, but of course, if it puts too much of a strain on the servers, it might not be a good idea.
Just wondering. 