How unique is the ethernet network adapter ID in WinRT? It is derived from the Mac address?
IReadOnlyCollection<Windows.Networking.Connectivity.ConnectionProfile> profiles = Windows.Networking.Connectivity.NetworkInformation.GetConnectionProfiles();
Windows.Networking.Connectivity.NetworkAdapter na = profiles.First<Windows.Networking.Connectivity.ConnectionProfile>().NetworkAdapter;
string nid = na.NetworkAdapterId.ToString();
No, the NetworkAdapterId value is a GUID and has nothing to do with the machine MAC address. You cannot get the MAC adress of the computer through WinRT APIs exposed for the Windows Store application type.