The trajectory for Bitcoin is likely spectacular. The world is spinning towards it.
But it could fail,but as per last events happened in September and 2013, its value will eventually rise after a time period .

second if governments get serious about banning bitcoin it can create huge effect on bitcoin though it can't completely destroy it,same scenario as of banning of torrents.,the main threat if from Chinese government a per now if it is able to conceal overtake chinese mining-farms, it would have control and could compromise the blockchain. But that would be very hard to do without getting revealed.

third ,If there's a disaster coming that can destroy the whole block chain or hack the whole bitcoin program it can affect the value of bitcoin or if exchanging apps and website runaway then users will loose all the bitcoin there are saving for future use.