A strong password is good practice under any circumstance. Hiding your MAC address won't keep it from those in the know who really want it, but it can't hurt.
I agree that
discovering a MAC address is not too difficult. But being able to turn around and use that info to sneak into a network which is granting access only to specific devices (hardware addresses) would take some pretty crafty doing. [but i guess the guys in that van around the corner probably have the gizmos to do that sort of stuff.
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