From what I read, the algorithm changes are aimed at content farms. So the affected sites would either be content farms or sites that have some of the characteristics of content farms.
I think we're moving away from the word "farm" as that was never used by Google. Some small sites have been hit as well (and "farm" would imply breeding for large quantity). I have seen 100 to 200-page sites hit. "Shallow content" might be a better phrase to use as Tedster suggested in another thread. Also, I am looking very closely at the phrase-based scoring [seobythesea.com...] as (for me) this penalty seems to be very phrase specific. I am trying to connect the "shallow" pages of my site with this phrase detection (perhaps via anchor text in my internal links?)