Research showing the lack of correlation between twitter hot words and Google or Yahoo zeitgeist demonstrates a key difference between the two and is important for reputation management companies to grasp.
Google zeitgeist reveals what words are being most searched for, but not which are being most discussed online. This is where Twitter is interesting: heavily tweeted and retweeted posts show that this is the real zeitgeist for the internet.
As commentators pointed out, search terms tend to be media driven. So Tiger Woods car crash is a media driven event and people want to know more. Twitter users tend to be less media driven and more discurssive in their approach to the Net.
If you want to get ahead of the trend: then follow twitter closer than you do Google.