I honestly don't think they care a huge deal about PBNs, but they dont' want these piece of shit ones out there. I've seen very blatant websites linking to each other for several years and I'm sure Google could have penalized them if they wanted to.
The problem is 95% of PBNs are absolute fucking dog shit, and that annoys the fuck out of Google, and rightfully so.
But if you have a PBN and your sites have great content, get natural links, etc, I don't think they would mind. I mean if you have 200 of these sites and that's the only links you have, that's probably a red flag.
But yeah, Google is all about the money. They want the big dogs spending money on Adwords. Here's my issue. I skip the ads because any shit site can pay to rank, even if they only deliver the product half the time. I have no idea. I go to the guys in the top of the search engine that have good sites and look like they're established. This is all tied in to their trust and branding, but how do you do it with adwords? I think that's a trend that's happening, more and more people are avoiding the ads because anyone can buy that spot. And I think Google needs to find a solution to it or their advertising profits are going to continue to decline.