Thanks for your response.
After my initial post, I came across another thread in this forum that deals in part with the same subject: http://electrical-contractor.net/ubb/Forum2/HTML/000981.html
As you say, the code spells out the minimum that is required to protect the wiring from the 1-5/8" screws of the drywall installer.
Para 300.4(D) also proposes that cable runs parallel to framing members be kept a minimum of 1-1/4 inches away. I believe that this is as much for the benefit of homeowner (attaching a heavy shelf), as it would be for the benefit of a kitchen cabinet installer.
In the case of the homeowner installing a heavy shelf, the homeowner could be expected to use a nail or screw which exceeds the typical length of a 1-5/8 inch drywall screw and seek out a stud to accept it.
The code seems to allow the homeowner a safety zone of 1 1/4 inches on either side of the stud in case he/she accidentially misses the stud.
Another paragraph I came across says:
"Also NOTE - Nonmetallic-Sheathed Cable and Electrical Nonmetallic Tubing. Where nails or screws are likely to penetrate nonmetallic-sheathed cable or electrical nonmetallic tubing, a steel sleeve, steel plate, or steel clip not less than 1.6 mm (1⁄16 in.) in thickness shall be used to protect the cable or tubing. "
This leaves the decision up to the electrician to imagine what folly the future homeowner(s) might create. This suggests that if 1) cable runs converge in walls or ceilings as they approach a distribution box, and if 2) these cables pass through holes in framing members, and even if 3) the holes are set in at least 2 inches from the outer surface of the drywall, and if 4) the electrician believes that a future home homeowner would likely want to install a heavy shelf in such a location, then the electrician has the responsibility to provide aditional protection with 1/16" thick steel plates.
For what its worth, I tried drilling a 1/8 inch diameter hole in such a steel plate and it takes very little extra force compared to drilling through wood and about an extra 10 seconds to pierce the steel plate.
These steel plates work perfectly in preventing a drywall screw from contacting the wire, but it would take a stainless steel plate to adequately discourage a naive homeowner in his or her attempt to drill into a dangerous wiring zone.
Thanks again for posting.