@thezerg: I agree with much of your posting - bitcoins have a large value in a situation without a reasonable reputational system in the darknet. They allow for transactions where only one side has to loose a reputation.
But once we succeed to estasblish a reasonable system of trust online, and once I have no longer any problem to trust a bank which works as a Tor hidden service, this advantage of bitcoins disappears. And, instead, real values (that means, online promises of trustworthy people to give you these values) will be able to beat bitcoins.
So, bitcoins are an important intermediate thing - they will be helpful to establish online trust. But, once online trust is established, with a lot of trustworthy online banks in the darknet, they will cease.
@Kazimir:
I guess old fashioned money like euros and dollars (I mean actual paper bills and metal coins) will still keep its purpose. When buying fruit at the market, they might come in handy (at least until you can pay with smartphones and QR codes everywhere). But the majority of all financial traffic takes place electronically. Today this is still done by/through banks, but with Bitcoin, we can do just fine without them.
Yes, we can. But, clearly, we have to make a certain step toward it - to give up legality.
If bitcoins become important enough, states will forbid them. But who cares - this will be similar to filesharing and copyright - the state cannot enforce it.
Nonetheless, there is a mental barrier for many people - they want to be law-abiding citizens.
But, in the long run, it depends on the ability of the law enforcement agencies to enforce such laws. Once they appear unable to enforce them, people will use them. Simply because it gives large enough advantages - you don't have to pay taxes for illegal transfers.