Robert_Charlton - 11:00 pm on Mar 26, 2013 (gmt 0)
It's a trademark issue. To protect their Google trademark, they need to keep "google" from being used generically to describe search.
From the article, my emphasis added...
Google wanted the meaning of the term ogooglebar — which describes something "that you can't find on the web with the use of a search engine" — to be altered so that it would only describe searches performed using Google's own search, something that the Language Council was not willing to do.
I'm assuming that the wording would be legally OK if it were something like...
...something "that you can't find on the web using Google"
...something "that you can't find on Google"
IANAL, but that's my guess.