PAN's are fully logged and investigated. The Capt and the controller who first acknowledges the call log reports.
Regarding the Wolf Like Pilot, you are quite right. MAYDAY can refer to Grave and Imminent Danger of an individual. Generally, my understanding is that it would only be called by an aircraft if it was likely to affect the safety of the plane itself, eg when a pilot has been incapacitated.
And although we deal with PAN PAX calls very seriously, one of the only times they wouldn't receive the highest priority is when there is another aircraft who is having problems staying up there in the first place...
Going on to Falconpilot's last. A PAN PAN Medical is certainly something I'd fully understand. If an a/c just declares "PAN..." the controller would always need more information anyway. In most cases I've born witness too, the pilots notify ATC as soon as they have a potential medical problem on board and a period of time later you receive a call like:
"VIR601, we're declaring a PAN due to our sick passenger..."
A bit non-standard maybe, but it's understood. The only time I've heard "PAN-PAN PAN-PAN PAN-PAN....." was when the aircraft itself was in trouble, and the pilots were a little more 'focussed'!
Seems like this post has actually done some good!!