This is a repurposed idea (Score 1)

back in the late '80's, Columbia/CBS experimented with watermarking to short-circuit our rights to make archival backups on early consumer digital recorders. Anybody remember the Philips digital cassette, or MiniDisc? The CD was to include a "watermark", which was basically a notched frequency in the output, that was supposedly inaudible. Problem was that it was 1) audible to anybody that wasn't tone deaf; and 2) detectable with the right equipment (e.g., scope). The idea was that when recording a "protected" CD, the device would detect the "notch" in the output and proceed to not comply with recording. And then there was the SCMS circuit (Serial Copy Management System) which wouldn't allow more than 2 or 3 (i don't remember) successive generation recordings . In those days, people that cared just bought professional DAT machines that didn't have this stuff (at first anyway).

I think the really interesting thing is the lack of full disclosure of these "use bombs". I don't think i'd buy a device if I knew it wouldn't work for its intended purpose, and I doubt the manufacturers would sell many of them. I just love the schizophrenia in this industry...