Yesterday, Google's head of search spam, Matt Cutts posted a video on Google's stance on using advertorials in a way to manipulate Google's search results.
As you can imagine, if you use advertorials and those advertorials have links to your web site - you must nofollow them or Google can take action against your web site.
In February, a major floral company was penalized over advertorials. And now Matt Cutts is making it crystal clear by posting Google's guidelines on it:
I covered this in more detail over at Search Engine Land.
There are folks saying, well - what about video content? Product placement. Do those have to be disclosed for users? I assume Matt would say yes. But product placement in videos do not manipulate Google's algorithms, at least not yet.
Forum discussion at Google+.