Compromised Hosts?

Nanogers - Would any broadband providers that received automated, detailed (time/date stamp, IP information) with hosts that are being used to attack (say as part of a DDOS attack) actually do anything about it? Would the letter have to include information like "x.x.x.x/32 has been blackholed until further notice or contact with you" to be effective? If even 5% of these were acted upon, it might make a difference. The question is... would even 1% be? Thanks for your opinions, DJ