So, who remembers the whole "Pakistan kills YouTube" debacle from February last year? Here's an article on the topic to refresh your memory:
Insecure routing redirects YouTube to Pakistan
The gist of the story is that Pakistan intended to block YouTube for their national network. They tried to accomplish this by advertising routing information with a higher priority than YouTube's own information, and which mapped YouTube's IP addresses into their network. This route advertisement propagated onto the internet, causing every server in the world to think that the way to get to YouTube was through Pakistan.
My question is: if something like that can happen accidentally through incompetence, could a malicious party do this deliberately? What safeguards are in place to prevent an attack like this? If Pakistan can do this to YouTube by accident, why can't Iran do this to Twitter on purpose?