http://en.wikipedia.org/wiki/Lexmark_Int'l_v._Static_Control...
But as Cory Doctorow points out, DRM can never succeed, because in order to sell a working system to your customer, you have to give them the encrypted content, and the decryption engine, and the key (otherwise, they can't use it). But if your customer is your attacker (or your competitor), you just gave your attacker the encrypted content, the decryption engine, and the key, so now they have everything they need to build compatible cartridges...
In the case of digital media, any weakness in the DRM means game over, because file sharing is so easy. But when talking about physical goods like printer ink and coffee capsules, it's a battle at the margins. They just need to discourage enough competition that their business stays profitable.
https://en.wikipedia.org/wiki/Lexmark_Int%27l_v._Static_Cont...
where the courts ended up rejecting Lexmark's theory that a particular way of making refilled cartridges work with Lexmark printers violated the DMCA's anticircumvention provisions.
However, you could still say that the printer companies are succeeding in using DRM to prevent competition (to some extent), even if it's difficult for them to sue companies like Static Control for circumvention.
