Apple's annual developer conference in San Francisco.
Apple's Services Suffering Another Outage as iCloud Sign-In and iTunes Store Go Down
Outages of Apple's services have been relatively common occurrences, with occasional iMessage outages being among the most noticeable for users.
Update: Apple has now expanded its outage list to include Apple ID and Game Center, although it indicates that iTunes Store issues have been resolved.
Update 2: As of 10:30 AM Pacific Time, Apple indicates that the last of the outages have been resolved.