I've been noticing the same thing, though some (not all) other websites are also running really slowly.
We had a problem at work last week that wound up being an ISP somewhere in the country that was having problems--not OUR ISP, and not the ISP of the institution we send data to on the web. (shrug)
You know how electricity works, right? Elves inside the wires push the electrons from place to place. And sometimes the elves are in a bad mood, I guess.