The sharing problem is no problem. If you give your email address for person A to person B, it will still work - but you and person B are now in the same "segment" together. That means if the address gets compromised than person A will have to rotate the address for both of you.

Still a damn site better than rotating the address for everyone in your address book. :)

As for the traffic caused by spam - I like your suggestion. Everyone use Segmail and they'll all give up. :)

-Andrew.