Wow I am surprised by that. I stand corrected, my apologies. That is what I get for taking anecdotal experience and extrapolating ;) I can't remember the last time I went to Google.com, but evidently heaps of people go there.
But I stand by my opinion that this is a weak response from Google.
Twitter seems to not care about SOPA, but Google claims to be actively working against SOPA - they should walk the walk if they are going to talk the talk. With this "message" on their homepage (which as jaysonelliot pointed out is not even seen by many people) they get the branding of being in support of an open web but don't have to actually take action the way Wikipedia, Boing Boing, etc are going to.
Just window dressing from the PR department. Disappointing but not at all surprising.
But I stand by my opinion that this is a weak response from Google.