Apple’s currently having an issue with multiple online services including all of iCloud, iMessage, and even the company’s Developer portals. Maybe the server farm in Maiden, NC overheated? It also appears that Apple’s iTunes store is also facing issues.
UPDATE: It looks like some of Apple’s services are coming online for some users, as iMessage and iCloud are now working for a group of users. Apple has confirmed the outage and has said that normal service will be restored ASAP.