Email's future: open or closed?

Kevin Werbach thinks that email spam will get so bad most people will resort to whitelists because spam filters won't be good enough. (A whitelist only accepts email from known parties and anyone else must perform some action that lets them contact you. Spam filters just block anything it "thinks" looks like spam.) Would this have a big effect on how people use email? Would it affect how the average user uses email? Even if spam filters don't filter everything, isn't filtering most things good enough not to have to resort to putting up barriers to communication? Will there be more effective governmental action on spammers as more of those in power get affected by spam, or is it out of legislative control? (via Techdirt)