Here is another question related to running NM wire through tight spaces:

I know that there are code restrictions on bundling NM wire together for long distances due to induction currents, wire heating, etc. How close to the wires need to be for this to occur? I can see the situation developing if they were tightly ty-wrapped together for several feet, but what if they were just strung loosely together, following the same pathway thru ceiling joists, access points, etc. How close to they have to be before you violate the code and run into problems with induction currents?