Netstumbler will pick up on a wireless network without you broadcasting SSID, this is the program of choice for wardrivers, I only know because I have done it before. With Netstumber, Map Point and a simple script, you can not only find networks....but you can create a pin point on map using GPS. Green for open, Red for secure. MAC filtering is simple way to keep people out, not bullet proof.......nothing is, but its better than nothing and keeps the casual wardriver out. With MAC filtering the user will go to other unsecure networks.
http://www.netstumbler.com/
Exactly. It's the same as securing your car or home from theft; let them go look for easier pickings. Sad to say, but you can hope that the crook will pass over your network because it's too difficult, and instead go over to your idiot neighbor's.