On a related note but somewhat off topic none the less,
I decided not to include forum in the list of subdomains to be ignored because I thought rightly or wrongly that this would have implications for my already google indexed pages which link back to www.example.com/forum/
Am I correct in thinking this? If google has already indexed the forum as www.example.com/forum/ and I allow the subdomain to be used changing it to forum.example.com will result in PR being split across what google will see as two different sites.
Is it better to use forum.example.com and then redirect everything from www.example.com/forum to forum.example.com with a 301?