a better way to charge for spam

Let me point folks at a paper written by a colleague of mine, Bala 
Krishnamurthy, on a better charging scheme.  It uses contingent 
liability -- that is, you only pay afterwards if someone thinks you 
sent spam.  See http://www.research.att.com/~bala/papers/shred-ext.ps
(or .pdf)


                --Steve Bellovin, http://www.research.att.com/~smb