Using an open network without encryption allows a passerby to listen in to all of your traffic. Unfortunately not all websites are using SSL yet.
Re:Open Wireless Movement
by mike_esspe on Wednesday June 11, 2014 @02:35AM
(#7876715)
If attacker knows network pre-shared key, and intercepted handshake, they can decrypt your traffic.
I guess I should have read the comments on this post: http://steve.grc.com/2010/10/28/instant-hotspot-protection-f...
The only use that I see for a standard-password approach is that it would circumvent some ISPs' terms of service that say you can't run an open network. But even then, a court may find that a closed network with a password like `openwireless` (i.e. as part of OpenWireless.org) is an "open network" anyway.