Earlier today, starting around 10:45 EDT, some people, especially in the Eastern US, found that they could not access Google sites and services, including Google mail. The incident lasted for about 1.5 hours, although the duration and severity of the problem varied by location. According to a post on the official Google blog, an unspecified routing error within Google’s systems caused the problem:
An error in one of our systems caused us to direct some of our web traffic through Asia, which created a traffic jam.
This is plausible. Trans-Pacific cable capacity is much more limited than trans-Atlantic capacity, and there are fewer alternative paths. Dropping in a huge slug of additional traffic would be quite likely to gum up the works. (There are backup links via satellite, but since satellites in geostationary orbits are 22,000+ miles away, the latency difference matters.)
The SANS Internet Storm Center also has a diary entry about the outage. (Right at the moment, SANS seems to be having some problems, but this link was correct as of ~20 minutes ago.)