In case you were wondering how this affected so many services at once, it seems to be because they targeted a server translating URLs to IP addresses. Behind all those fancy browsers everything uses IP addresses, which are practically formed of a bunch of random characters so they're not really very user-friendly. When you head to the URL in your browser, the browser asks a DNS server what IP address corresponds to the URL, and then heads to that IP address. In this case, the DNS server was the target of the attack and thus you couldn't get the IP address of any service from that DNS server. Technically this means that none of the services were down, you just couldn't find their addresses.
I recently read of a report that someone's been trying to figure out how to take down the whole internet recently. They've been testing different important points and how well defended they are. This, it seems to me, is simply continuation to that, and worryingly enough, it seems pretty easy to take down even pretty big portions of the internet. In a few years, an attacker with enough resources could probably take down the whole internet for a good while, and I wouldn't be surprised if they were able to do it even now. Not a scary thought at all, eh?