We have reported about the structural USB weakness that makes all use of USB plugs a security risk
viewtopic.php?f=22&t=3414&hilit=badusb
So to avoid this computer AIDS we need protection and now there is a solution; the USB Condom!
So now you can charge your phone on any computer without having to fear that it is hijacked or you can allow someone to use your computer to charge the phone without having to fear that your computer is going to be hijacked.
You can have the USB-condom for $9,99 (yes that is $10 - but some smart ass thinks you will get fooled if we call it 9,99 - and he is probably right
) 
So if you want to charge your device there is protection.
If you actually use USB to transfer data - and need it for that - then you still have a problem, and should only use your USB devices with your familiar hardware and never connect it to anything else.