Bill Gates thoughts on Bitcoin:
"Are you excited about the potential of Bitcoin in systems like these as a way to keep fees low and have the system work robustly in the global sense?
There’s a lot that Bitcoin or Ripple and variants can do to make moving money between countries easier and getting fees down pretty dramatically. But Bitcoin won’t be the dominant system. When you talk about a domestic economy, [you must have] the idea of attributed transactions, where if you sent it to the wrong person you can actually get the transaction reversed. [And a traditional system] doesn’t have this huge fluctuation where the value of your account is going up and down by a factor of two. We need things that draw on the revolution of Bitcoin, but Bitcoin alone is not good enough."
Well, NuBits elegantly solves one of those two issues as of this moment. I guess that multi sig transaction can solve the remaining issue, if you want it to be reversible.