> See poorly configured DNS servers and ISP's failing to configure their networks properly - so traffic with a source address which is not part of your allocate

> See poorly configured DNS servers and ISP's failing to configure their networks properly - so traffic with a source address which is not part of your allocated IP block is not allowed to leave your network. It is not that hard! It may not be that hard to set things up this way, but very few ISPs configure their network with this restriction.