The biggest issue facing bitcoin, is that there's nothing to stop a "bitcoin 2" from entering the market.
A lot of people here are mining, trading and we're all happy as Larry that the price is going through the roof.

The problem is that once mining difficulty hits a plateau, people start considering energy costs etc, then people will start to drift away from mining. Currently we're at the peak, GPUs sold out etc etc - but we're all still 'making money' and watching our stash rise in value.

Right, so what happens when that grinds to a halt? We all throw our GPUs away?
Just takes somebody to create something similar and we'll all rush off to get onto the "ground floor" of whatever's coming next. It'll probably crash and vanish without a trace, but tell me you don't think anybody else is going to try?

All economics are based on scarcity, bitcoins are 'scarce' - but only within the market of bitcoins. Currencies themselves aren't scarce.