not a scenario in Old Akro's post, it was antenna failure
I've had 2 GPS antennae failures, which is why I list it. We use GPS based dataloggers almost daily at work and have regular antennae failures. I regard GPS antennaes as a consumable item.
For as long as I have been flying (since te early 70's) a fundamental tenant is to have redundant systems. But now CASA / AsA seem to be turning their back on this philosophy because its inconvenient for them.