UPDATE: Microsoft has confirmed all services are restored.
It appears that Xbox Live is down. This was confirmed by a tweet from Xbox Support. We’ll keep you posted on the latest as soon as we hear it. Let us know in the comments if Xbox Live is working for you!
We have run into an issue with the Xbox Live service, and are currently investigating. Stay tuned for status updates. ^PS
— Xbox Support (1-5) (@XboxSupport) June 20, 2013
[Via: Xbox Support]