SAN FRANCISCO  YouTube was back up two hours after Pakistan, in an act of information provincialism, inadvertently made the video-sharing site inaccessible to users around the world Sunday afternoon.

The blackout left network administrators and Internet activists wondering on Monday how Pakistan’s actions, meant to restrict only its own citizens from accessing YouTube, could have such widespread reverberations  and whether such a disruption could be reproduced by someone with more malicious intent.

The incident began Friday, according to reports, when the Pakistani government of Pervez Musharraf became worried that a video clip attacking Islam might generate widespread unrest among its Muslim population. The government asked the Pakistan Telecommunication Authority, which oversees the country’s Internet providers, to cut off access to YouTube for the country’s estimated 8.2 million Internet users.

That action is not unusual. China, Morocco and Turkey have all reacted to potentially risky material posted to YouTube by blocking access to the site within their borders.