Charles Hudson has a very thought provoking blog post on google vs twitter theme. He says database of intentions (google) is more valuable than database of musings (twitter) for now.
I agree with the basic thesis of his article, though I would characterize twitter more as a database of activities/interests. The other point being, I would frame the comparison as static vs realtime web, though search quries are a part of realtime web too so google is a player in it as well.
Then there is facebook, which fortune says is taking over our lives, compiling database of relationships. This provides a context to both database of intentions and activities/interests.