One problem I have noticed with using the Web to find certain quotes is that there are often several incorrect versions floating around.  For example, what did Homer really say?  I have also noticed this problem with the "memorable quotes" section of imdb entries, as well as the multitude of song lyric sites out there.  They are close but not exact.  The Web does not provide a way to correct all of the sites at once, nor is there any way to judge trustworthyness.  One could perhaps argue for Page Rank as an indicator, but popular is not the same as correct.  Seems like an interesting problem.