I think this is rather silly of Google. Here's my view on it.
In Firefox, prefetch is on by default. It should be off by default. These things should always be opt in, not opt out.
The average user won't even know that prefetch is happening and won't think to read a FAQ to find out about something like that.
So Google are utilising prefetch on the search results? Let's say the first result returned is a site with hundreds of pornographic images on it, and the browser starts caching that without the user knowing. Say also that they are on dial up. Now let's say that the user clicks the fifth result in the search listing. The broswer has just downloaded a whole bunch of rubbish the user didn't want and it's clogged up their machine and maybe also eaten into a monthly transfer allocation.
Why should the user have to suffer degraded pc and net performance for something that they haven't chosen?
I think that prefetching is wonderful idea when implemented properly on a site I have already opted to view. But not in a search page -- that's just dumb. At the very least, there should be a way of blocking certain sites from utilising prefetch, but allowing others.
I generally have applauded Google's innovations over the years but this one sucks big fat ass.
*hates Toni Y for life*