Google Blog: "When you do a search on these browsers, we instruct them to download your top search result in advance"
You know, this smells a little bit like Google doing what this post from Raymond Chen outlines.
Google is making everybody's website with a high google rank slower because somebody "might" click on it and we want that to be fast. It's nice that you can opt out on your end, but what if the website owner wants to opt out of this behavior because google searches are slamming their site with incoming requests that people aren't following through it.
I guess if the google search algorithm is perfect then there's no problem, because people will always choose the top link... but how often do you "feel lucky"?