Also the author shouldn't rule out Halon's razor[1]. Advertising the wrong AS is often caused by incompetence or mistakes of network engineers. Note that I'm not a network engineer (I'm a linux monkey by trade), but know you can do BGP AS path filtering[2] ala ACLs to prevent a rogue/incompetent entity from advertising routes that dont' belong to them. If more ISPs would simply lock down their routing infrastructure a bit more, a lot of these types of attacks would be rendered mostly void.

[1] http://en.wikipedia.org/wiki/Hanlon's_razor

[2] https://ftp.apnic.net/meetings/22/docs/tut-routing-pres-bgp-...