The biggest threat is surely running out of Bitcoin addresses.

Now that is funny. Do have even the foggiest idea how big 2
160 is? No, you don't (and really, I don't either).
Goverment! Look, friggin Bolivia banned Bitcoin!!
Bolivia? Really? You are concerned about Bolivia? Really?
GHash.IO which is a joint consortium of various Bitcoin miners, now control more than half of the mining activity, a phenomenon which by some circles assessed would be a threat to the system.
I remember when the DeepBit mining pool was the 51% boogie man and everyone was sooooo concerned about them. Where is DeepBit now? Anyone seen them? No. Same thing will happen to GHash.io eventually.