Microsoft (just one example here, for the sake of time):
The "reuse address" socket option is supposed to allow the address/port otherwise tied up by closed, but lingering, sockets to be used again in a quickish manner instead of waiting several minutes. It is not supposed to allow multiple open sockets to do the same thing. In fact, that is NEVER EVER supposed to happen, but it can done on a Windows machine.
The MAC address filtering feature on wireless access points is supposed to limit what wireless clients can connect to it, not filter every single packet regardless of how it arrives (ethernet or RF). Granted, wireless MAC filtering is far from bulletproof security, but that kind of stupid design makes it even more useless.