They may have been able to win on other grounds, but in this case, they won for this reason. CPHack makes the software worthless as protection. This is at best contentious. I would argue that it is bad practice because email is not reliable enough and not secure enough. It violates several of the important aspects of what it means to serve a legal document, such being sure that the named person received the document, that the document arrived intact, and the person receiving the document knows that he received it.
Email is, however, clearly a useful adjunct communication media.
This is clearly a question for the courts to decide in a more deliberate manner. The court found that parents should be able to lock their computers from prying eyes. The court relied upon software licensing with restrictive clauses as the way to protect the software that locks the machine. I'll argue below that this causes further problems. Schools and libraries that use software like NetNanny or Cyber Patrol without fully understanding them and the sites they allow and restrict are irresponsible in their public stewardship.