Why does everybody keep thinking governments can't tax bitcoins... on whatever you buy, the company you bought it from, still has to give 21% VAT (here in Holland, if customer in EU based only) whenever your salary gets paid in bitcoin, government is still going to grab the amount of tax they want, before you get your bitcoins in your wallet. Its just going to make the life of accountants a million times simpler, txn in the blockchain, it happened
Double-spend, impossible to hide. (and will not be possible very easily)
Still not sure if they'll survive when they can no longer print money. (since nobody accepts their money anymore)