Why: Relevancy. Speed of Indexing (seemingly as soon as it is published). Speed of results being displayed.
Straight up blog search is no longer a game for startups. If you don't have serious cash; aren't setting up major distribution partners; aren't innovating fast and furiously on the UI, analysis and feature set; and talking to established internet companies about being absorbed, you won't be around much longer.
Yahoo, MSN, Ask aren't far behind.
Although we all knew this was coming, it is kind of sad in a way for all my friends and readers in the blog search world. Your job just got a lot harder.
It is time to differentiate.
Blog Search Companies: What are you gonna do now?