Check out your referral logs.. notice a pattern? If your logs are like mine, a HUGE percentage of your hits are coming through a search engine (Google, Yahoo, MSN)... Here is 3 minutes worth of referral logs from my blog...
In a world where a good percentage of your content is dynamically created and displayed in Ajax or Silverlight, how can you enable search engines to find your data?
Well, a bunch of folks across the web have been doing some thinking on this. Jonathan Hawkins recently did a session at mix on the topic and posted some thoughts. Nikhil also discussed the issue in his talk at mix and posted some interesting techniques as well.
ASP.NET Futures CTP has features to enable you to have multiple code driven dynamic sitemaps. This can be used for ASP.NET, AJAX and Silverlight web applications. There is a quickstart tutorial.