The governments don't want bitcoin to succeed, it goes against central banking interest.
That is the biggest threat to bitcoin.
The other currencies are far more easily controled, due to knowing the founders etc and there not being as such a limit to how many units of a currency there are.
Bitcoin is amazing in and of itself just because its limited at 21million already. That as a currency is huge, it adds stability to its value that no other currency other than pure gold and silver have right now.