E-mail postage stamps?

The NYTimes is running an article that highlights what the pundits consider to be the solution to the spam problem today. By requiring that an e-mail cost money, a penny maybe, the plan overlooks the fact that the cost will vary depending on which country the email is sent from (1 penny ~50paise in India). My spam filters seem to be doing well at separating the chaff from the corn and Mozilla's Bayesian filters apparently are even better than the commercial offerings by Yahoo! and MSN so I'm not gonna be a proponent of this scheme. Unless of course, I have my own email server and have to sift through the spam myself or my filters stop working...