I have a lot of addresses I've created asking for donations and I don't always think about tracking them every single place that I leave them. I envision a time when I will retire or loose or otherwise want to move a receiving address from one bitcoin client to another. It would be nice to have an easy way to export a public/private keypair from one client and import it in another. Perhaps there'd even be a way to email them or send them between two client's RPC channels.
A followup to this is to also be able to share my bitcoin address book for outgoing payments that I send to others.
