Picture this: You're at a café with your laptop and latte in hand, getting ready to review new sales leads and the quarterly financial projections. First you hop on the free Wi-Fi that the shop's management provides. Then you connect your laptop to a projector so that the entire café can take a look, and finally you hand out some printed copies of your confidential product specifications to the other patrons so that they can follow along.
That may sound ridiculous, but if you're using public-access Wi-Fi without taking the proper precautions, you might as well be asking your coffee compatriots to partake in confidential company information.