> the barrier to buying a domain is so low This suggests that one way of making spam unprofitable would be to require any domain which sends email to put up a

> the barrier to buying a domain is so low This suggests that one way of making spam unprofitable would be to require any domain which sends email to put up a bond of $100 which is forfeited if any of the big four email providers decide that the domain is sending spam. To make this acceptable to public opinion, the forfeited bonds would to go directly to popular charities, and all existing domains would be automatically grandfathered in, so there would be no extra cost for any current business or user.