Plazer lets you get the most out of Plazes, a location based service which is still in beta. The Plazer looks for the hardware ID of your local network (MAC ID) and checks whether it is already in the database with an address, so we can plaze you at that location. That is all it does. The Plazer is NOT Spyware or Malware. Sending your router's MAC ID to Plazes does not make your network or your Mac vulnerable to any attacks. Still your MAC ID is not accessable to anyone and is only used for identifying your network.
Plazes lets you discover nearby locations or people based on where you are and recommends things you should check out or people you should meet based on your past whereabouts.