I agree in principle with what you say...

But I think in view of the intractable problem of creating a formula that keeps ever-evolving spam methods at bay, there's also a place for some manual "weeding" - particularly in the case of serial spammers like these ****** sites. Sure, 888.com can open up a new domain tomorrow, but having spent millions on advertising this domain name on the tube and TV, getting it kicked out of google would make them sit up and pay attention. If spamming was seen to be counter-productive, webmasters would stop inventing new methods of achieving it.