Please note that this is my personal oppinion.
Basically bitcoin will fail if it succeeds. Lets say Bitcoin succeeds. Everybody starts using it. Now the Problem is that bitcoins have a fixed total number which cannot be increased by anything at all. So if it succeeds then people will start hoarding bitcoins because as the economy grows and the demand for bitcoin as a currency increases the value of bitcoin keeps going up. As a result people will hoard them even more and as they hoard them, bitcoins will increase in value still further since there is a fixed number and the demand will be increasing more and more. Eventually people will stop using them as a currency because they won't be able to find them in sufficient quantities for everyday use. At this point the hoarders will have something that has no intrinsic value (unlike gold or silver hoards) at all. As an instinct these people will then try to sell their bitcoins for real money which they won't be able to because as I mentioned above bitcoins have no intrinsic value and therefore the demand for bitcoins will decrease drastically. And the more the "value" of Bitcoins decreases the more people are trying to sell them which will make the wohle process even faster.
I'd love to hear your oppinion about this topic :)