It could happen. A staged event killing a lot of people. "The terrorists used bitcoin. Therefore bitcoin is evil."
The world bank would then pay the media to show it as evil.
True, the media spins stories for the right price. However, even if the "banks" were to drive their enormous financial resources into smearing BTC....what would that accomplish? If anything, it would push BTC further into the black market/darknet and possibly even encourage its use and proliferation. The ensuing media frenzy surrounding BTC would also give the currency free advertising to the masses and encourage people to look it up and even download the wallet client to start using it.
1930s era Prohibition....'nuff said.