This is a horrible idea. Yes, it would result in increased focus by some people on speed, but probably the same people who focus on "SEO". So now content relevancy has yet another adversary in the battle for SERPs. There's a LOT of really incredible, original content out there written by amazing people who do it in their spare time and don't give two shits about their SEO or the speed of their server, and now that content is going to slip further down the rankings because it takes 2 seconds to load instead of 100 ms? No thanks.