Two problems that have been troubling people with Google searches are:-
1. There are so many mirrors of Wikipedia out there and Google indexes all of them; so when you do a Google search the search results are cluttered up with links to different copies of the same text. Sometimes, half the results in a search are copies off of Wikipedia.
2. Also pages that are on eBay are indexed, and Google keeps these in its index far after the auction it picked up the keywords from has ended. So when you do a search, the search results are cluttered up with links to eBay pages where the auction has expired so has nothing valuable for the searcher.
I hope the people of Google group reads this and find a solution to this problem.