I've been following this closely, as well as the 4chan /b/
thread.
Looks like Google pulled the plug.
Edit: They went down for 5 mins, probably due to the massive
amount of /b/tards.
Seems like they have cleared up the mess already. Given that
it's a public holiday for them today (Independence Day), I would
say the response is pretty fast, but not fast enough. I mean, it
has given enough time for some to develop exploits that wipe
system32 directories off IE and Opera users (assuming the exploit
on /b/ is working). As those on FacePunch has mentioned, they could
simply shut down the server or disable the comments system entirely
first and take their own time to fix it instead. But of course,
it's Google - they probably had some red tape to clear before they
could implement the necessary changes to the system.