In a recent video, Matt Cutts spoke about Google's efforts to target black hat spam and link networks.
Quote "We’re also looking at some ways to go upstream to deny the value to link spammers–some people who spam links in various ways. We’ve got some nice ideas on trying to make sure that that becomes less effective and so we expect that that will roll out over the next few months as well.
And in fact, we’re working on a completely different system that does more sophisticated link analysis. We’re still in the early days for that, but it’s pretty exciting. We’ve got some data now that we’re ready to start munging and see how good it looks and we’ll see whether that bears fruit or not."
Today in a series of tweets, he confirmed that Google took action on a number of link sellers and link networks. There is some speculation in the comments at SearchEngineLand about some of the networks that got penalized.
I don't think any legitimate SEO is going to risk his reputation or losing a client on spam techniques.