Some users are stating that the Los Angeles datacenters are the culprits for the connectivity issues. However we want to caution users that Blizzard has made no official statement about their datacenters.
There is also plenty of evidence that states otherwise. It's important in these cases not to assume things with incomplete data. However Blizzard's technical support staff does have complete data, and appear to be hard at work fixing the issues.
Blue poster Claudiog is seeking more information from the community on the technical support forums. In particular he's looking for traceroutes from affected users. Head over to their forums (ignoring their own ads) and help them out if you're struck with these issues.