Pardon my ignorance here, but wouldn't it be much simpler if the so called "tier 1" networks were to do the filtering work so that none of downstream BGP peers would see the bad announcements ? If some network in italy sends out some bogus route for a site, this should be blocked by a few tier 1 networks instead of by everybody at the bottom of the tree. Yeah, that would mean that folks in italy and whoever would have direct connections to that italian network would accept those bad BGP announcements, but the rest of the world would continue to work. "tier 1" networks like to brag about their importance within the internet, perhaps filtering bad announcments should be a responsability assigned to them, and which would further differentiate them from lesser networks.