I do not seet it as a problem, so what if I have the same private key in many wallets? Actually for me that is the case, because I store my wallets in many places on the internet. Encrypted of course.
That's backup-copies. I have those, too.
But say I give a privkey to a friend as birthday present. He imports it at some point and I still have it in my wallet. Now there are two active bitcoin clients showing the balance of that key. If one of the two spends the money, it will disappear from the other client, also.
So my friend or I will wonder "where the hell my/his money went"
That's only if you gave your friend an address generated by the bitcoin client, or an imported address.
If you generated one for him with "vanitygen" or some other bitcoin address generator, and never imported it to your own wallet, you could freely give a private key to a friend and intentionally "lose" the key yourself so that you cannot access his funds.
Give people the freedom to import/export as they want. Sheesh, this is getting as bad as government. "Well, I know what the people SHOULD have, and that's more important than what they want."
I was making no assumptions; I was under the impression that molecular was pondering a way to gift his friend a "pre-loaded" bitcoin address/privkey without being able to accidentally spend the coins himself. I was merely pointing out that there is a way to do this, albeit not with standard, unmodified client alone.
I'm all for freedom to import/export as people want.