A brief article that might freak out companies worldwide, and maybe some individuals, too: The New York Times Magazine ran this brief piece that follows a white-hat security cracker/consultant in checking out the swiss cheese of networks.
Unfortunately, because the guy had such legal qualms, we don't see the real skinny; he only talks about it. Sure, a lot of information passes over unprotected networks, but it's the complementary ability for people to join a network and then attack machines, many of which certainly feature unpatched security flaws that allow the largest disruption.
Nonetheless, the ease by which the fellow extracts passwords and views networks may signal some mainstream alarm.