I can usually rationalize a code issue by defining a hazard but my wife stumped me yesterday. She has an old panel that is installed over a 11 1/2" shelf. We both know that is a working space violation but I can't explain the hazard. There is plenty of elbow room around the panel itself and the height is OK. The 11 1/2" shelf still allows adequate approach and even provides a counter top to put your tools on. It is non-conductive (wood with polyurethane).
After seeing it, I am thinking about putting a shelf under mine ;-)

Not knowing the actual panel conditions.
And we all know that codes are usually generic in nature meaning it would be impossible to write a code to meet all actual conditions.

I can give you one example where it is a hazard.

To just open the panel and look it might be fine. You are standing at arms distance away.
Now try to add a circuit when you really need to put your body up against the wall to take out the ko and fish the wire in. If the shelf is there you need to kinda lean against the wall with your head and your torso is against the shelf. If something happens like a fault or whatever what do you do?
You can't just drop to the ground because the shelf is in the way.
To get away because you are bent over you will need to push yourself away against the wall.
When I am working something hot I don't even like scrap wire cuttings on the floor let alone the end of the fishtape reel laying at your feet.

Just to be the devil's advocate I might say NFPA70E probably prohibits you from fishing into a live panel ...

... but I see your point.

Most of the provisions in Article 110 of the NEC are derived directly from OSHA. OSHA and the NFPA has been greatly influenced by the insurance industry.

So, I agree with your point. There is not a direct and evident hazard associted with lack of working space about electrical equipment. However, having required working space removes liability from the underwriter's in the event someone gets hurt while working on the equipment.

It's a shame, but I think this is where our industry is today.

That's right Bryan. See who is in charge of the whole ball of wax in North Carolina:
http://www.ncdoi.com/OSFM/default.asp

Thanks for the link. Very interestng stuff!