Well, I've experienced it myself on a previous car, but it's been mentioned a few times by "Honest John" the motoring journalist for the Telegraph.
It is (apparently) one of the most frequent reasons for breakdown callout - most people assume it's knackered, give up and call the AA.
Still don't know how it works though - like you say there seems to be no compression and I don't understand how that's possible without some sort of relief-valve or similar.