Only way Bitcoin fails is if governments seriously saboteur it by preventing banks from processing fiat transactions in relation to it, but the gamble is that once the establishment tries to assault Bitcoin, the counter force and backlash will serve to propel Bitcoin to the level of a household name and away we go.
This didn't work out to well for online poker. If major government intervention happens as you describe...SELL, SELL, SELL.
Au contraire, I first found Bitcoin as a result of the poker 'black friday'. The weak point in online poker was the bank funding re third parties. That got me thinking about how governments can (and do) influence the banks to effectively shut down undesirable industries. The beauty of bitcoin is that it can't be shut down that way. Although exchanges can be attacked or outlawed in individual countries, it is impossible to shut down face to face currency exchange or bitcoin sales. There is no central authority to control, unlike the poker companies.
I use bitcoins to play poker, even though I don't need to (live in Europe) just because I can.
BTCBTCBTCBTCBTCBTCBTCBTCBTCBTCBTC
I know man, I was there. I felt like a part of me had died.
My thoughts are they can absolutely cripple Bitcoins growth via the banks. Not to mention pushing away all hope of legitamate US business getting on board which will just stagnant Bitcoin altogether. It would continue in the black markets and underground poker sites, etc. sure....but they can do major damage. But hey that's negative talk...its' too early for that. Let's celebrate the rise and hope for the best. 
EDIT: I stand by my sell order should something major come along.
