Oh, and as for what they did -- lots of stuff. It looks like they were originally just adding sporadic bogus entries that would link to their paid websites. Then, probably sometime recently, someone went through and automated the whole thing, deleting all the real entries and adding literally tens of thousands of bogus ones pointing to their customers.

It's standard wikispam stuff: they stuff a real website full of their BS, all as interlinked as they can get it, to drive up the Google ratings of their customers. Unclear how well it actually works, but it's big business nowadays. It's why wikis are in a constant arms race against the vandals these days...