I once saw the consequence of two PCs on the same LAN with the same MAC address. (How? Some foul-up by the NIC manufacturer. I suspect a whole batch of boards out there with that same MAC; we'd bought two of them).
It wasn't pretty. Looked somewhat like an intermittent NIC failure or cabling fault. One went down whenever the other came up ...
Anyway, it occurs to me that causing a MAC collision in some environments might be regarded as an actively hostile act ... espionage, or even sabotage. Even if not, it will most certainly attract attention if one's random address just happens to be the same address that some local system will try to use in a few minutes time.
Is there a way to detect this and back off as soon as it happens, before the other system's owner gets annoyed?