Even though my long-term (4-6 years) outlook on Google is $800, Google had become a media favorite, owned by far too many individuals, institutions and hedge funds. High growth in a large cap like Google is rare and when everyone including the doorman at the hotel you're staying talks about owning the stock, you know its time to leave the party before the cops come busting in.
If you don't mind short-term pain, stay with Google. Else, short it to $300 and cover. I wouldn't be surprised if it goes down to $280 at this point, but its unlikely.