I used to work for a large, well-known hosting company whose name is taken from a book of the Bible. They didn't have to many spammers or pr0n sites in their space when things were booming, but now they're among the worst for hosting spammers.
There are network providers all over the country that are as bad or worse. I recently ran across one that had a
A lot of spam is sent through China by contract with network providers there, and through South Korea because it's the open proxy capitol of the world, and there is a very large and well organized spam ring operating in eastern Europe as well, and it seems soundly connected to US spammers. The spam business has gone international in a big way.
In none of those places, including the US and Canada, generally, is spam illegal, so it's never necessary to bribe any government official into looking the other way. It's just easier to pay off the ISP to look the other way in some countries, but again, that's pretty easy in a lot of places in North America too. When the economy goes down, pink contracts go up. Many companies and individuals will do just about anything to survive, and network providers are certainly no exception. For every one that will cut a spammer's connection as soon as they notice, there's another that will happily sell the spammer as much bandwidth and IP space as he wants. Then they pass that space on to some other unsuspecting customer, who finds that she can't send mail to a lot of places because that netblock is in every RBL - good, bad, or ugly - in the world.
As much as we rightly despise spammers, those who sheeld them and knowingly sell them bandwidth and colo space are just as bad.