Apple likes to make things as easy as possible to join WiFi networks, especially when the network isn’t password protected. However in one reader’s case this isn’t a good thing but rather a major headache:
Is there a way to RESTRICT joining certain wifi networks to certain OS X user accounts?
When using my MacBook Pro, I have two basic OS X logins. One for known SECURE wifi networks, and one for INSECURE wifi networks. The problem is that Airport settings always remember the INSECURE network, and almost always tries to connect my SECURE OSX login to the INSECURE wifi, at which point Mail (or other apps) start up and shoot my logs/passes across the air for all to see.