What I've seen is improperly installed Wirenuts, especially with more than two wires.
I recommend twisting two wires together and then twisting additional wires around this, then cut the ends square.
When you're done, stress test the setup by using a room heater and measuring how much the voltage drops when it's switched on.
50' of #14 should drop 1.3v from one conductor end to the other, @ a 10A draw. Measuring the neutral drop is safer.
More than this is contact resistance within the Wirenuts.
The box may limit the fire hazard from this but you'll have flaky appliance performance.
If anyone makes a Wirenut with a small test prod hole in the small end, I'd buy it.
That way you can troubleshoot using a VOM without taking the nut off and disturbing what may have been a perfectly working connection.
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
https://en.wikipedia.org/wiki/War_of_the_currents
There was also a fight over FM radio.
http://www.google.com/search?client=safari&rls=en&q=fm+radio+patents+widow&ie=UTF-8&oe=UTF-8