I investigated it a year or so ago as an online game I played switched to only accepting bitcoins and no longer paypal payments as the game designer was so convinced it was the future.
However the way one generates bitcoins or "mines" them is having a computer running a background program. This has led to people setting up entire houses with overclocked (pushed to their limits) computers inside.
We live in a world with a very large power crisis looming and still rely very heavily on non-renewables, the idea that someone would then create a "currency" that gets hundreds of thousands of computers around the world "working" on abosolutely nothing. wasting so much power and computer life so they can get a few "coins".
I remember the Seti@home project which was similar except the computers processing was used to help search for ET, analyzing results from hubble etc.. Bitcoins processing is pointless, its just wearing computers out for no reason.
I wouldn't be suprised to find out the CPU / GPU manufacturers had helped back Bitcoins, they must've been rubbing their hands together in glee when they read how it worked.