If you forgot your charger, or if an AC outlet isn't available, charging stations can be a handy option if your phone battery needs a top-off.
However, these devices can be hacked and could represent a security risk. Depending on how your phone is set up, it is possible to have malware uploaded to it or information downloaded via the USB cable when you plug it in to charge it.
Charging-only cables are available, but that means carrying an extra cable. Or you could turn off your phone completely while you're charging it - but that's inconvenient.
Another option is a charge-only adapter. There are available - here's one: http://syncstop.com/
You just plug it in to the charging station and then plug your phone into it. It turns off any data transfer and prevents data up/download while your smartphone is plugged in.
Pretty handy - and safe.