This loopback adapter should not be assigned any LAN address, because as a loopback adapter, its interface is visible and usable only on the machine itself. A common example and use (and mistake) is for example to bind your webserver to this loopback address. When you do this, then webpages are accessible by any one or more addresses you want to assign it (typically 127.0.0.x) but not accessible from the network.