Matt Cutts has posted an interesting observation regarding ASP.NET 2.0 and search engine optimization. Aparently in some cases, ASP.NET's Url rewriting is emiting 302 redirects (instead of 200 sucess), causing Google to ignore these pages.
My site relies heavily on Url rewriting, via the fantastic UrlRewriting.NET library. I checked it with Fiddler, and everything seems to be in order. After reading through some of the comments, it seems that it may just be an issue with Community Server. It's good to check things out though.
If you're using Url rewriting, take a few minutes, download Fiddler, and check out. If it's indeed a problem, I highly suggest the UrlRewriting.NET library.