Your MP3 recorder isn't required to be certified under stringent regulations (which are there for a purpose) including being able to survive crash, fire, submersion at high pressure, etc.,
I'm guessing the point some are making is that for incidents such as the AF dversion we are on about here there's no need for a robust system...then again it would still have to interface with the aircraft's audio system so there would be certification issues.
However fundamentaly we increasingly live in a society where many seem to think the number one priority in
any situation is to have a recording, or access of a recording, of an event. I assume the idea is this can then be used for a variety of purposes ( monetary, regulatory, increasing hits on social media outlets). Frankly I'm not keen on moving much beyond where we are now.......guarantee privacy, fix the blame culture, then it will be easier to make long period DVRs acceptable.