Google has quietly updated their Webmaster Guidelines, the little or no original content section. They added a example reference there for "low-quality guest blog posts." Brian was the first to spot this change.
I would not be surprised to see manual actions for guest blogging, not link specific, but content specific penalties.
Here is a screen shot of the page before:
Here is a screen shot of the page now:
Google has gone after guest blogging for link purposes most recently but now they seem to be making a statement with this change for content spam purposes, not just link building. Google has taken action numerous times for guest blog link networks and other guest blogging for links.
Now, will we see many penalties and manual actions for guest blogging specifically around content spam and not specific to links?
Forum discussion at Google+.
