Evan_83 :
The problem with Bitcoin, and the other upstarts is that eventually the market will flood with this type of currency.
Why is the US Dollar (still) the dominant currency in the world? Why is ebay the dominant online auction site? And why is Facebook the dominant social network? Because they all act as platforms which derive their value based on the number of others that you can reach.
There have been plenty of other social networks and plenty of other online auction sites. But a major reason they can't displace the big guys is that they paradoxically can't achieve comparable value until they reach comparable scale. So, there's a huge practical barrier to entry, even if the mechanics of copying an ebay or a facebook aren't necessarily that big.
If a cryptocurrency ever emerges as a currency (i.e. rather than primarily as an investing asset), then it could reach the dominant position of something like the US Dollar, where it's incredibly hard to displace just because so many people accept it and so many things are priced in terms of it.
I thought Bitcoin would reach this phase, but a couple of the core maintainers basically staged a coup and steadfastly refuse to increase the protocol packet size, which is needed for it to scale to the level of an actual currency. They've successfully managed to shut down any attempts to fork the currency or otherwise defy their will. So, I think it might eventually die off. We'll see.
I still believe in the idea of crypto-currencies. It'll happen, one day. There's too much demand and too many people trying to do it. Somebody will get it right, and reach that critical mass first. There might also be a second and maybe even a third player. But the bigger those top couple cryptocurrencies get, the harder they'll be to topple.
Probably the major risk they face that doesn't apply so much to conventional currencies is that of an exploit. Possibly involving quantum computing, I wonder...