For now the entire PKI in bitcoin is closed for users. I propose make it more clear at least for JSON-RPC. It will be possible to create bitcoin paycards and such. All is required is to convert private (and maybe public, too) keys to base64 encoding and printing them to stdout and also implement creating private key in wallet.dat by importing such base64-encoded value. I guess public key may be easily calculated from private so when you export private you have no need to export public.

The purpose of this feature is to make possible creating deferred payments when you don't know (or don't want to know) whom to pay to. You give or leave the private key which has some amount of coins somewhere and recipient then withdraws money to his own wallet. With such functionality one can make a competition and the winner gets that key and receives money so you shouldn't worry about that. You send money to the new address, export its private key and place it to the page which is shown to the winner. And so on.