I'm super excited. I have one bugbear - why so late? It would have been late in 2011, when we put up a slideshare guide to bad SEO, Google should have start this much sooner.
Google effectively (naively maybe) allowed a billion dollar industry to grow up creating crappy spammy content sites and blogs. Software that spun content (takes one or two articles and turns them into multiple "unique" posts). The buy-a-link industry is huge - especially if not measured at source.
In 2010, we predicted that SEO audits (for bad SEO) would be a major feature of the future SEO landscape. Essentially, we used to come across sites that had bad link patterns that were really ticking time bombs that could go off at any minute. No SEO agency needs that on their watch. There's a lot of 'bad' SEO out there and bad is a variable term with varying depth and breadth. An example could be a site with very bad on-site SEO at a basic level - for example, obvious bad use of Page Titles and internal links. Not using Google Webmaster Tools. But having 10,000 inbound links!
I guess there are thousands of agencies that happily charged customers a couple of grand a month and the only work was to charge the VISA $200 to India/Pakistan to pay for spam.
Doesn't affect you? What about all the work @Blacknight has to do to keep this forum spam free? What about all the "Guaranteed #1 Position" e-mails we get? This is all off the back of that - Google took long to clamp down.
It's also getting easier. Fighting a tough website for ranking? Are they using lots of rubbish, cheap blog post links and comment spam? Report it...