#1 is < 1-1/4" to framing edge w/o using a nail plate at bored holes and corners and at staples generally above multi-gang boxes... fires from fasteners shorting romex or MC.
#2 is unprotected cables w/in 72" of an attic access where crossing truss bottom chords or joists... occupants place boxes on cables & slide storage items over the cables.
#3 is mis-identified or un-identified circuit breakers on loadcenter directories... occupants work on circuits they believe they have de-energized, or are unable to locate the correct breaker quickly.
#4 is undersizing conductors... numerous ways... leading to fires from overheated devices and equipment
Bill, you also mentioned most common problems [vs. violations], and there are a few "problems" I see daily doing inspections. First is misunderstanding or lack of knowledge regarding the basics, like grounding and overcurrent protection, and not just by homeowners. Thinking that wires shorted by a nail or something will instantly trip or blow the OCPD, or that the instant a wire accidently touches a pipe or gutter, that it will trip or blow the OCPD.
Another common "problem" is lack of respect for the potential of fire and electrocution by homeowners, or the tradesmen types that know just enough to be dangerous, jacks of all trades and masters of none, or even improperly trained electrical apprentices or journeymen, whatever there background. Guess we're all guilty of that at times, working equipment hot, shrugging off some nail plates that are needed at hard to reach locations, not double checking terminations.
And here's one more "problem" probably beyond the scope of your question [but I'm bored tonight]. How about roping multistory office buildings, for instance. This new 2002 rule change allowing NM a few more stories indicates to me that lawyers have taken over the code making process. I can't believe that went through. The only possible explanation I can imagine is cable manufacturers buying votes or threatening lawsuits. Step one, we pushed dirt up over 50% of the bottom story of a 4-story building so we can say it's only a 3-story. Step two, we changed the code to allow a few more stories. Step three for 2005 will probably be to prohibit the use of MC and EMT in buildings over 1 story. I don't know who was on that CMP, but somebody caved.
