There is a bug in the URL Rewriting engine of ASP.NET 2.0 which leads to
search engines dropping (or not indexing) sites using URL Rewriting. While
not specific to Community Server, it maniftested itself more so in CS
communities at first. Here, Scott Watermasysk presents a workaround.
Links to the original problem are included.
Full story at http://scottwater.com/blog/archive/2006/07/17/ASPNET-20-UrlRewriting-Fix.aspx