Google has put out a bunch of new videos (seven, to be exact) about various types of web spam. So far, we've looked at a trio of them dealing with unnatural links. You can find them here.
This one is about thin content, or content with little or now added value. This is essentially the kind of thing Google's Panda update was designed to attack, so if Panda has been a problem for you, you may want to pay attention.
Doorways, thin affiliates (Cutts says this is the most common by volume), thin syndication (which he says is also very common), and scrapers are examples he discusses.
While talking about affiliates, he notes that the things that Google considers to be adding value include adding original insight, research, analysis, reviews, or videos.
On what you should do if you get a message about thin content, he says you can remove such content or actually add value to it. Anything original is bound to help.