Bitcoin mining, which is at times profitable (especially when using a botnet), wastes electricity for absolutely nothing. The same effort could be put into, for example, folding@home, or into something enjoyable at least.
That, in my eyes, is reason enough to consider bitcoin to be evil, even without getting into any other details (such as assassination markets). The number one problem with libertarianism is the tragedy of the commons, and waste of energy due to bitcoin is a good example of how libertarians do not even try to respect the commons. On the plus side, the mining is capped and so the amount of damage is limited, so an argument could be made that it is necessary evil.
Force polygons of equilibrium structures
2 years ago