Topsy, a social search engine, states they've managed to index ever tweet ever made...

http://www.searchenginejournal.com/social-search-engine-topsy-indexed-tweets-existence/68681/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+SearchEngineJournal+%28Search+Engine+Journal%29

WOW!

...and more to the point, why?  I'd suggest that MOST, the vast majority of Tweets, or largely useless.  last night I tweeted obscure '80's references while blathering about what music I was listening to.  Really. Truely. Irrelevant. ...and yet, in that se aof noise we all create, there remains some nuggets of value.

Topsy - you want to impress me? Sort that stuff, dump the garbage and show me the real gems. ;)