The Firefox add-on Pirates of the Amazon inserts a "download 4 free" button on Amazon, which links to corresponding [Pirate Bay] BitTorrents. The add-on lowers the technical barrier to enable anyone to choose between "add to shopping cart" or "download 4 free". Are you a pirate?  
...a net-art project supported by the Piet Zwart Institute and moddr_ medialab.
Site (with QuickTime/Flash video clips) experiencing high traffic.  
UPDATE (5 December): ...Lawyers for promptly served the students’ Internet service provider with a take-down notice, and on Thursday the students complied and removed the tool. (New York Times)  
The extension is still in the wild...  
[cc: it's the arts]