We used to advise people to do banking and other important business over their cellular connection when using a mobile device, since it is generally safer than connecting with a public Wi-Fi network. But even that isn't always a safe bet. Researchers have demonstrated how a portable cell tower, such as a femtocell, can be used for malicious ends. The attack hinges on jamming the LTE and 3G bands, which are secured with strong encryption, and forcing devices to connect with a phony tower over the less-secure 2G band. Because the attacker controls the fake tower, he can carry out a man-in-the-middle attack and see all the data passing over the cellular connection. Admittedly, this is an exotic attack, but it's far from impossible.
A mix of features and price make a good VPN, but plenty of bad VPNs masquerade as good ones. Look for articles written by trustworthy sources that discuss the merits of each service based on its features, versus simple rundowns and user testimonials, which are almost always polluted by a combination of fanatical users and corporate bootstrapping in attempt to get their names out to potential customers.
In short, it's time to start thinking about protecting your personal information. That's where virtual private networks, or VPNs, come in. These services use simple software to protect your internet connection, and they give you greater control over how you appear online, too. While you might never have heard of VPN services, they are valuable tools that you should understand and use. So who needs a VPN? The short answer is that everyone does. Even Mac users can benefit from a VPN.