This is entertaining reading. Although I don't know how pervasive this issue is, from the chunk i have read so far I can see why he was concerned that it was relatively trivial to have a target system accept anything identifying itself as a printer and being able to inject malicious code into the machine.

I was going to make fun of him wasting his sabbatical on hacking a printer service but I gotta admit I'd have fallen down the same rabbit hole if I stumbled on it. It's a cool hack.