Right now the primary way of obtaining bitcoin is trading for fiat currency. The difference between your Euro example is at some point people started receiving their salaries in EUR, while this will not happen in the foreseeable future with BTC, even if adoption increases as those of us bullish on BTC think it will. Companies will start offering employees the option of being paid in BTC only after their revenues are coming in in BTC in meaningful numbers. BUT, and this is a very important point, the current size of the bitcoin economy cannot support a meaningful amount of purchasing power; $1.something billion with the majority of that being held does not go very many ways in a multi-trillion dollar economy; so in order for this reality to happen, the price of BTC would have to be exponentially higher than it is now.
Very true - but unfortunately it (the adoption of the euro) was the only near-ish example I could think of in real life which I can equate to. Even though it was 10 years back, I can remember it well when I got my first pay check in euros. With the euro being 1.27x times the old Irish punt, it "seemed" like I got a payrise, when in reality I was getting exactly the same "money" as before. I didn't mean to suggest that the adoption of BTC would be the same, only that it would be similar from a psychological view point. i.e. How many goats can I buy with 1x BTC is all that matters verses USD or Euro or magic beans.
Yeah, I'd also agree with that summation that for it to replace fiat it would need to be "backed up" with a heck of a lot more than the 1xbillion USD that it's currently got - but remember, some 12 months ago it was down in the 80-100 Million so it's not impossible - just unlikely.
Me? Like everyone, I'm hoping my paltry few BTC's will explode and that I can pay off some of my mortgage in fiat :-) Well, we can all dream can't we?
Slightly off topic: I remember reading a SCI-FI book "Red Mars" some years ago where the author had a great description of the value of money on Mars. Must have a look for that again.....