BTC isn't a real currency, I can't pay my taxes with it
Right. Nor can you pay them with gold, euros, pogs, flooz, sports trading cards, or a zillion other things. Government authority in the US accepts dollars. So what?
I can't pay any of my debts with it and nobody is forcing anybody to accept it.
You can buy software, web hosting, domain names, precious metals, gamble, clothes, electronics, dental service, legal service, books and fuck all else with it. Just because you can't pay your cable bill with bitcoins yet doesn't mean they aren't useful to others.
It's not backed by gold, silver or the promise of anybody with the means to back it.
Bitcoin is backed by the compute power of the bitcoin mining network, the bitcoin protocol, and modern cryptographic techniques. Can a 51% attack break it? Maybe. Will a flaw in the protocol kill it? If one is found and exploited, certainly. How about some breakthrough in cryptographic analysis or technique, like say quantum computing? Another possible killer.
In fact, it's designed to result in crushing deflation in a way that no currency is. If there aren't enough USD, you can print more, if there are too many, you can take them out of circulation when they come back.
There are some issues here. Hard drive crashes and no backup of your wallet? Barring some heroic drive recovery, or crypto breaking technique (which would likely break the system as well) those coins are gone forever, further lowering the number of potential bitcoins. But really, not much different than cash being destroyed.
A bitcoin can currently be broken up into 10^-8 pieces. There is room in the protocol for that to be increased. There could be 1 bitcoin in the world, and the pieces would still be useful.
Seeing how an elastic money supply controlled by private bankers has only caused larger boom/bust cycles since the Federal Reserve System was implemented, I'm at least interested in how the bitcoin system plays out. Even if it eventually dies, lessons will be learned, and the next iteration will be better.