I've become more and more paranoid about using WiFi that I don't manage. Because of that, I always use a VPN when I am using WiFi other than at my house, my work, or my inlaws. While I am using OpenVPN with a 3rd party VPN service, I don't recommend that for most people because it is a lot more complicated to setup. I highly recommend Cloak for folks wanting a really easy to use VPN service for Mac and iOS. It's dead simple to setup and they have various kinds of plans for the sporadic user vs the power user. One of the things that makes it really easy to use is that you can set it up to automatically connect if you are connected to an SSID other than ones you put as your "safe" networks. This means that when you walk into Starbucks, it will automatically connect and you won't have to remember activate it once your connect to WiFi.
They offer a 5 GB plan for $2.99 per month or an unlimited plan for $9.99 per month. If you use IAP purchase through the iOS app, you can prepay for the year for $99. They also have a weekly pass option through IAP that is handy if you just need it for a conference, etc. Your Mac, iPad, and iPhone can all share the same account and data bucket. Security is something we should all take seriously, but Cloak makes it easy and inexpensive.
Download Cloak on the App Store.