The one that worries me the most is environmental (power cost, gpu/asic manufaturing).
It also sucks for projects that actually needs to use computational time for real world problems like folding@home and seti@home.
And it sucks big time for PC gamers.
I am worried about both things, in fact I touched on it in regards to manufacturing all this hardware to calculate virtual numbers that have absolutely no value in reality.
As the eco-system evolves hopefully the environmental impact would be reduced significantly.
It does indeed suck it's turned into such an insane hype machine and get rich quick scheme - but it solved a real world problem that is going to become more and more acute. The war on cash is real, and having a digital cash to fight back with is necessary if you value freedom or privacy on any level.
Ask wikileaks how well relying on banking access went for them. And like it or not, plenty of grey and black markets exist.