I will have a wiki and a forum, so I thought it would be a good idea to have:

www.example-domain.com
wiki.example-domain.com
forum.example-domain.com

Then I started thinking about how google views this what it means for the site as a whole in terms of ranking and the like. I know (from another site I have access to) that the Google webmaster information sees the subdomains almost as a completely separate site (almost as if the domain name is irrelevant).

What are your experiences on this? Any thoughts appreciated :)