Google has updated search to find Content Farm, but nothing is perfect.
The Farming of Content
What constitutes a content farm is open to debate.
A general consensus is that the label applies to websites that lift content almost entirely from other sites. However, that's also true of sites that churn out patterns of words that satisfy Google's algorithms, using search engine optimization (SEO) techniques.
Here is an example of a post I wrote yesterday that is copied by another site.
FRIDAY, MARCH 4, 2011 AT 12:23PM
Greenpeace has a site specific for unfriendcoal http://www.facebook.com/unfriendcoal.
When you Google Search for “greenpeace unfriendcoal t-shirt” a content farm comes up #7
Whereas my original content comes up lower.