... probably most of the Abuse issues (especially via email) would continue to be ignored. Noone wants to handle that stuff. But someone(s) must handle that stuff.
the underlying question is, "or else what?" this is an assymetric-benefit situation. when folks ignore reports from noncustomers the people they are hurting are those noncustomers. as sean and others have pointed out, there's no incentive-stick in that equation. someone asked me privately:
and why would anyone care about branding? what would it gain them?
until theres financial penalties for being a bad netizen, there wont be any incentive to follow the rules.
if it were a checklist item for government/military/largecommercial contracts then you can bet that the sales team in every large/medium isp would beat the drum internally to ensure qualification and compliance. given the somewhat direct relationship between insider (customer) service, outsider responsiveness, and network uptime, this isn't a hard sell. what's hard is figuring out who can host the brand and what collection of people (network owners and their customers) can be trusted to define it. i'm thinking the new NRO (joint project by apnic/lacnic/ripe/arin) might be the right place to home a responsible-network-ownership branding program.