Nick suggests,"Twitter's search query numbers include "searches" from Twitter apps such as TweetDeck and Seesmic that are actually just automated calls those apps send out every few minutes to populate columns users have set up to see tweets on certain topics...." they are," Maybe "topic updates"?"
He is right, however, I'd suggest for a number of Twitter users they have been seeing more topic updates from Twitter search everyday than they do in major search engines like Google. Personally, I may not look at every query from a client Twitter app, but I look at enough, and also have them automatically running, to the extent that it's easy to keep up with what's going on in Twitter and wider communities.
I'd suggest that topic updates in a date related search engine like Twitter search are a new mainstream approach to searching, and a significant one. I want to see the steam of updates that happen around a topic. This need to see topic searches is one reason why #hashtags are so popular on Twitter, humans are curious about the latest news on the topics they love.
Having automated searches set up is a function that Twitter search and third party apps do well, if you will Twitter is the leader in automated topic updates. They might not be beating Google in other areas but they do have a lead in this important new approach to search.
My suggestion to Twitter, or other 3rd party app developers expand on the automated topic update function, give people the ability to filter searches, and remove junk within a topic update, deleting posts that include keyword references or deleting the profiles of individual Twitter users for a particular search.