MAC addresses, unlike IP addresses and IPX addresses, are not divided into "host" and "network" portions, so a host cannot determine, from the MAC address of another host, whether that host is on the same layer 2 network segment as the sending host or a network segment bridged to that network segment and, if it's not, cannot determine the MAC address of a router that is on the same network segment as the sending host or a segment bridged to that network segment and that can help route the packet to the destination host.
In english; Only the Internet service provider you pay knows your MAC address, but I suppose they can provide that information if hacked or simply asked.