What changes would you make to stop spam? - United Nations Paper

[Marc Perkel]

I'm writing a paper that I'm submitting to an Internet Governance Forum 
of the United Nations. Keeping in mind that free speech and freedom is 
important, what would you change in the world to stop spam? I'm looking 
for things that are actually possible and practical. Suggestions can be 
anthing. My thoughts include things like requiring ISPs to provide 
better firewalls for end users, requiring Microsoft to provide more hack 
protection even for pirated versions of windows, ways to keep people 
from impersonating other users, evolving the SMTP protocol ....

Looking for more ideas. Paper is due tomorrow.