You forgot the most damaging one: - security

It is impossible on a practical basis to secure any significant amount of cryptocurrency. Even the most secure known methods of storage have been compromised [1], and computer security has reached a state which means everything is hackable. Every Bitcoin exchange I can think of has lost some significant amount of coins to hacks. I see no reasonable solution for this problem.

[1] http://leaprate.com/2015/02/is-bitcoin-safe-yet-bter-exchang...

EDIT: I have always liked your posts on bitcointalk.org