Demand Accountability from ISP's? (Score 1)

Maybe I missed something, but aren't attacks like this only possible when an ISP doesn't enable outbound packet filtering? i.e. just like they have incoming router rules saying they will accept packets for their domain (192.168.0.* as an example), can't they also have outbound routing rules that say I'll only xmit packets that originate from 192.168.0.* Is there a compelling reason not to enable this? Can we start some kind of movement to educate the ISP's that they need to do this? If most of the ISP's could do this, we'd be able to discriminate against the ISP's that dont on the BGP level (where you have to have an accountable routing address). Kind of like people used to block agis.com email because it was a spam haven. I'm certainly not an expert on this, can someone pick this idea apart? Thanks! Bill