Interesting case to raise. Reminds me of the NFL terms voiced after every game about the broadcast being for private use only. I imagine that if their terms don't already include a clause like this, they can try to suggest that a toolbar tracking user clicks is violating the terms.

Very murky waters. If Google starts complaining that other people are tracking their users, they might end up educating users about how much they and their advertisers track.

...I hope DuckDuckGo figures out a way to capitalize on this brouhaha...