Just to add a little scientific documentation to the horrors of puppy mills, here is a link to a scientific article about a puppy mill Yorkie in Portugal whose parents hadn't been vaccinated against ANY diseases. The 8 week old Yorkie puppy died of canine adenovirus type 1 a few days AFTER it was sold to its new owner. Includes necropsy photos for those who are not faint of heart. Let me know if it's behind a pay firewall, and I'll post some of the text and the necropsy photo.
[WARNING: GRAPHIC PHOTO IN PDF LINK BELOW] http://vri.cz/docs/vetmed/59-4-210.pdf