Did you enable the screen lock as well? If so, it's simply not being used at all possibly.
Clean install requires a password if FMM is enabled, no?
Yeap, iClod is waiting for it to connect to the internet to lock it out. That's what I am hoping for... but I did not have a guest account, so to be able to connect it they have two options: hack my password (unlikely) or do a clean (offline) OS install
If they do a clean OS install without connecting to the internet (feasible), and after that, before connecting, they turn off FMM, it's done... they can then connect to the internet and iCloud will never know that Mac is mine.
After that and as long as they keep FMM off, they are good to go.
Hey Gurus: PLEASE correct me if I'm wrong!