I leave them all enabled because I use them.
Bluetooth is on when I leave my office so it pairs with my headphones.
NFC is combined with tasker to switch the state of my devices automagically when I put them down in different rooms. NFC stickers are pennies and it's an easy way to set your phone to a profile suitable for the room you're in
Wifi is always on because I'd rather use that radio than 3G because it's much lower latency for web.
3g is on because I can't always get Wifi.
Yes, there's a potential for attack in all these channels, no it doesn't bother me. There's risk in every activity, if you're aware of it and plan accordingly, there's no reason not to partake. I really love the capabilities of newer devices, I use them and they make a lot of things in my life a little easier, a little faster or a little more capable.
Sure it's not in everyone's risk appetite, but it is in mine. For me the pay off far outweighs the risk. Not everything is, I won't use a credit card in the US any more for example. (not until they get chip and pin at least)