Carbon tanks

Consider that they are used by firemen... in burning buildings... that may collapse on them... and they're approved by the NFPA. 
They are actually aluminum bottles wrapped in carbon fiber then coated in an epoxy resin. 
They're pretty durable.
With that said, I would not even go near abusing them! You want to treat them as if you life depended on them. There's a helluvalotta potential energy there. 
That's not to say that the manufacturing process is not without its faults and very very few will get through that may have some type of defect. It's probably something like .0001%?
Tom
 
I had the same concerns when I first got into PCP airguns. Honestly, I still have a bit of fear dealing with this much high pressure air, but I think this just makes sure that I am always careful and alert.

I take great care handling the equipment. I visually inspect my tank, valve and hoses when I can. Also buy the best equipment that you can afford.

Yes you are correct, some dive shops won't fill carbon tanks, they claim insurance reasons.

There is some great info on this thread that you should check out:

http://www.airgunnation.com/topic/carbon-fiber-tanks-weeknesses/