Both iMessage and FaceTime were down earlier this week for several hours, though Apple's Services Status page does not indicate any problems as of 7:30AM Pacific time.
Update: Apple has updated its system status page indicating issues with both iMessage and FaceTime.
Update 2: Apple's status page indicates that the issue has been resolved as of 9:07 AM Pacific time, although we are still seeing scattered reports of problems.
Article Link: iMessage Again Down for Some Users [Updated]