Yes backing a currency in gold will give confidence. Yes backing a fractional reserve with a military and resources will give confidence.
If bitcoin can TRULY deliver on its promises as a payment transmitter, than it may just get enough confidence to become a currency as well.
As it stands now however, it looks like a speculative commodity.
However, it's easy, simple to undermine confidence in fiat currency - just overissue and prevent conversion to other forms.
Can confidence in Bitcoin be removed? Not sure about that one. Would banning trade in it like gold can be banned remove all confidence? Very hard to say, and something to watch.
If we end up in a place where world governments have fallen to the point where we no longer trust their money, and have switched back to gold, what industry is going to still be around using gold?
I just don't see this.
If there were a single global universal fiat currency, that might not be the case, but ethereal isn't one.
I think we may see this if bitcoin becomes too popular. I mean, it may be too late by then, but why not try right? Oppressors gotta oppress.
This just means for Gold, you effectively have a Put option for a very small percentage of what it's currently trading at, instead of 0% of what it's trading at.
That said, if it becomes too much of a liability to store (hackers, taxes, transmission) in the future without the growth, then it'll lose confidence. I feel like any problems with security though would only become a reality when it would hit mass appeal.