Facebook can't know the MAC address of my router from my friend being here and using facebook. At MOST they could know my IP address, but everyone has Dynamic a

Facebook can't know the MAC address of my router from my friend being here and using facebook. At MOST they could know my IP address, but everyone has Dynamic addresses nowadays and that's a useless data point. Google _does_ know router's MAC addresses, because they mapped BSSIDs when doing streetview mapping.