I'm pretty sure Jeff lives in the US, but judging from his activity, I'm not sure. He seems to be alive at 2am(Central) and I also see him at 9am. Sure, this is 7 hours difference for him to sleep, but doesn't he have things to do like eat, look after his hygene and other things?
Clearly, a human would not have such crazy posting habits, and therefore I propose that Jeff is an alien that hates bacon and does not sleep.
On a different note, I don't see Joel often, but it's usually at around 1am.. Clearly Jeff and Joel are the same person! Hence the whole SO operation is a cover up for illegal rep gaming!! No one is safe!