Over the years I've been witness to a number of cage bolts loosening. Those of others and yes, a few of my own. I think people are hesitant to wrench down on them due to the variety of materials involved. You can be pretty safe in tightening a stem bolt to 5-6 Nm but a carbon cage might have a spec of 1Nm for a bolt just one size smaller. Throw in Riv-nuts, butted tubing at its thinnest, etc. and general absence of published specs. Anyway, if folks are plagued by loose cage bolts, I'd suggest blue Loctite.