I guess the blog search engine shakeout has started: Mike Arrington is reporting that PubSub is going down:

Blog search engine PubSub had massive layoffs today after last minute merger discussions with knownow fell apart. It looks like a shutdown is imminent.

Google survives as a search engine via the ad business. I subscribe to a bunch of PubSub generated feeds, and I've had no reason to revisit their website since I set those feeds up. The feed items they find don't come with ads, nor do they slip ads into the feed separately. When I browse an item they found, I go to the item - not to a summary on their site.

Push all that together and it means that there's no revenue. If you give away a service, you need to find some other way to monetize it - and PubSub just hasn't.