Apple is currently experiencing a number of service outages that it says affects "less than 1% of users." The affected services are iMessage, Photo Stream, Documents in the Cloud, iCloud Backup and iPhoto Journals. From the Apple System Status portal:

Multiple Services - Less than 1% of users are affected Users may be unable to use iCloud Documents, Photo Stream, iPhoto Journals, or Backup & Restore. Users may also be unable to send or download attachments in iMessage.

Thankfully it's isolated to a small number of Apple customers, though it has lasted for around six hours so far. Any kind of outage is frustrating to those it affects, are you one of them?

Source: Apple