I have been doing some thinking on the results of the google search
site:amazon.com "kindle edition" .
http://www.google.com/search?num=100...on&btnG=Search
There are now 5,670 pages in the Google cache that have the words "kindle edition" on them. It's a very diverse collection of books. There are more technical manuals and textbooks than I have ever seen outside of PDF format. This by itself could make the Kindle the market leader.