Google manual action penalties due to links for freebies

A month ago, we reported that Google had issued warnings to bloggers over providing links in return for free products to review. 
Now it seems that the penalty actions reported over the weekend were directly related to Google’s warning last month.
Google advised bloggers reviewing goods they’d received free of charge to nofollow any links pointing readers to sites where they can buy the products.
As reported by SER, Google’s Webmaster Central Help Forum contains plenty of questions from bloggers who have received penalties over the weekend, like this one:

The post by Sammi Penni in relation to the penalty notice shown above has been replied to by John Mueller,Webmaster Trends Analyst at Google.
John confirms that the penalty is related to the warning about nofollowing links:
There’s absolutely no need to nofollow every link on your site! However, those that are there because of an exchange (such as a product or service for a review) should have a rel=nofollow on links to the product, to their sales pages, and to any social media profiles that are linked because of the review. Also, it’s always a good idea to clearly label these kinds of posts for your readers too.
There are other, similar exchanges in which John advises that the penalised sites should unfollow links which may have been added in return for free products. 
The entries also reveal that the bloggers in question seem to have been unaware of any need to unfollow links, and several said that they hadn’t received any payment for links.
As with warnings over guest blogging for links and other such instances, these pieces of advice are often followed by a penalty. I guess it’s a way for Google to show it means business, and to send a wake up call to others.
As SEO Barry Adams pointed out to Search Engine Watch recently:

In addition to the blog post, we should expect Google to start dishing out penalties to bloggers that have obvious link placements. A few high profile penalties should suffice to instill an overpowering fear of linking to companies among bloggers, at which point Google’s work is done.
Google doesn’t actually have to figure out the difficult bit of algorithmically identifying commercial link placements; they just plant the seeds of doubt, and let the blogosphere’s inevitable panic do the rest.

The question here is how much Google knows about the relationships between brand and blogger in these instances. I can see plenty of unfollowed product links in these blogs, but I’ve no idea of the relationship behind them.
Maybe Google knows something here, and hopes the resultant panic will be enough to deal with the issue.
However, for hobby sites who are reviewing products for fun and adding links because that seems to be the natural thing to do for readers, it seems they’ll have to tread carefully.
As Barry also pointed out, this has implications for what brands can do:

Google is now clearly redrawing the lines of how a company’s promotional efforts are allowed to influence the link graph. It seems Google interprets any promotional activity that results in links as an attempt to manipulate its search results, which begs the question what a company is actually allowed to do in Google’s eyes to boost its online profile. 

Inevitably, bloggers will follow Google’s advice rather than risk a penalty.
Google clearly has no way to police such links on a large scale, so it is relying on bloggers to unfollow links. Many links will be unfollowed, whether they’re genuine or not.
Source: ClickZ
Link: Google manual action penalties due to links for freebies