[Walt Fricke]

Plus, per Carroll Smith, what keeps fasteners from loosening in most applications is adequate stretch (or, if you will, torque to produce stretch) to exceed the stretching loads imposed. If the bolt has sufficient clamping force to do the job, it won't loosen.

There are exceptions - 6 bolt flywheels on 70.4mm cranks being one, due to some unfortunate harmonics at 8,000 or so RPM. Even then, enough stretch seems to solve the issue, although we all use a little carefully applied red stuff just in case.

I don't think rod bolts come loose. Oiling is the main problem, and there is the odd rod which breaks, or the odd bolt which missed out on quality control, or which wasn't actually fastened to the right torque. Or which is stressed beyond what it was designed to do (like money shifts, for instance).