Prefetch shoved down your throat whether you like it or not, analytics accuracy out the window along with your bandwidth and the functionality of your page since it starts playing behind the scenes.
OK, so the first page loads fast, what if the second doesn't? Fooled the surfer into thinking your site is screaming fast when it isn't.
Wonder how many little sites using hosts that limit bandwidth will end up displaying "Bandwidth Exceeded" like Google gives a rats ass if your site gets seen or not.
The only real issue I have with concept of preload is the idiot PhDs that originally shoved the function into browsers just randomly load crap instead of giving any control like "rel=preload" so we can actually make the process make sense for our sites.
Here's the real rub - Chrome OS is a wireless broadband/wifi-based OS, so preloading pages automatically will put more strain on already overloaded wifi sites like airports and other high volume wireless locations. If those Chrome laptops catch on they'll be prefetching the available bandwidth into oblivion.