We're generally supportive of efforts to make life easier on legitimate marketers. But I don't know if it's a good precedent to set for Internet service providers to charge per message for guaranteed delivery. That doesn't seem like the best way to handle spam.
If there were a good, user-level solution out there, we wouldn't be so worried about passing anti-spam legislation. ISPs can filter and block hosts who send almost nothing but spam, but at the user level there isn't much you can do that also wouldn't affect legitimate e-mail.