How is it "responsibility", when the actions of a third party (in this case Mt Gox) can cause your bitcoins to be lost?
Theres nothing the end user could do to prevent the theif?
I Think Bitcoin is great in that you can *select* the responsibility. You can select if you want to be responsible for your own bitcoins, and thus apply your own security to them. (and not be forced to have a friggin' 6 digit pin code and a security token for a bank account with only 50$ on it, thats pretty stupid by the banks - security should at least match the value protected by the security)
But if you select that you don't want to be responsible for your coins, but have someone other to be responsible for them, you need to have a protection scheme that would recover the assets if this "someone other" does lose its assets.
Like banks have state Insurance, there could be a blacklisting scheme called "bitcoin Insurance", but this are as said, ONLY applied to entities holding assets for a
large number of usersLike Mt Gox, and such entities.
The system could work in some way with a blacklisting scheme, that you can opt in for, but only when personally accepted by Gavin/Satoshi or someone high in the bitcoin scheme, OR a Public vote.
To get in the system, you need to maintain:
-large amounts of Money.
-identity should be known to the authorities (a licensed operator) or personally to Gavin/Satoshi
-have a user base for the service that is large too.
-The Money owned must be spread out, you can't have 10 000 users that own 0.00000001 bitcoin and 1 user owning 10 000 bitcoins to get into the system, it must be spread out so every user of your service have depoisted a fair amount so the value that you hold, its ownership are spread out by the service.
A limit for each user could be maintained too, so when X % of the stolen Money has been recovered, then each user of the service gets back up to X BTC, of the Money they depoisted, the rest of the recovered money are destroyed and the blacklist are revoked.
There must be schemes to validate that the user did use the service and have coins depoisted too.
Like the state bank Insurance in the EU/Sweden. If the bank goes bankrupty, you can regain up to 100 000 € of your depoist.
USA have a similiar scheme with
http://en.wikipedia.org/wiki/Federal_Deposit_Insurance_Corporation (FDIC) that insures up to $250.000 of the owners Money for US banks.
Bitcoin needs a similiar scheme to recover thefts and losses.