Approaches such as limiting the number of addressees would kill mailing
lists with little or no effect on spammers.
Approaches such as billing for number of outgoing items won't work without
cooperation from spammers (yeah, right.)
How many spammers need to turn up dead to serve as a deterrent to those
conteplating doing it?
How many spammers need to turn up dead to reduce their population to a
managable level?