"It's not about whether you can hear the difference between MP3 and Lossless. It's always blindingly obvious."
Double-blind testing doesn't support this claim. At semi-reasonable bit rates, most people cannot tell the difference. At high bit rates, almost nobody can tell the difference.
The problem with mp3 isn't about whether or not you can hear the difference. It is, as you seem to allude to at the end, about the chance of the mp3 being converted back to PCM and the re-compressed using the same or a different lossy algorithm. That really does start to get into the audible realm.