In running circles, the aformentioned icebreaker is almost always certain to come up in any conversation. The proverbial talking point's saliency is relative to the overall goals of the person addressing the query. Thus we could surmise that for some runners this question may seem completely irrelevant, while for others it takes on near-reverent status.
People run for different reasons. Some run to lose weight, some to beat themselves. Some run just for the cardio, while some just like to hang out for the company. That given,the key concept that I wish to postulate on pertains to when exactly does running cease to be fun, and our inherent competitive streak starts to kick in? Let us try to explore two distinct possibilities.
Conditioning. Could it be a simple matter of conditioning? Under this assumption, the moment a runner gets into better shape the PR's would essentially be transmuted into the be-all/end-all of the running experience. However, if this were accurate, then how could most people confirm the existence of the "blatantly out-of-shape yet uber competitive" runner types? Just some food for thought.
Personality. This goes to argue that people who have strong personalities tend to be more competitive towards their race results. However, I have personally met several runners who have an aggressive, competitive mentality off the road yet are completely timid on it. And vice versa as well. So what gives?
The looming question of where runners get their competitive edge is a tough one, bordering on a philosphical, paradoxical precipice. On that note I can offer you no answers. After reading the following entry though, I am hopefully leaving you with chunks of inquisitiveness that you could bite off and chew. I don't have any formulas, but your inputs could enlighten us towards a greater understanding of why we do what we do. With all the running going on, it never hurts to stop for awhile and think. Do it often enough, and you'll never look at "Pare, Ano PR Mo?" in the same light again.
Just some food for thought.