The Harmful Consequences of Postel's Maxim
tools.ietf.org
tools.ietf.org
Right now, for me, the worst "offender" (I.e. "faithful observer") is USB type-C. Hook up two high speed thunderbolt devices using a cable that supports only USB 2.0 speeds and it will "work", but slowly. There's currently no way to tell which cable is which by visual inspection.
I can see why this is a triumph of engineering and back compatibility, but I can also see why it's a problem.