I think it would be extra-clever to generate a contact card for the user after sign up. Then they can just import it into their address book. ...of course this

I think it would be extra-clever to generate a contact card for the user after sign up. Then they can just import it into their address book. ...of course this relies on the user having vCard set up to open with the address book that they actually use. And it is surprising how broken most user's setups are.