Well, eavesdropping is not really the correct term, as the people pontificating at coffee shops usually do so loudly so that others may bask in their perceived intellectual glory.
The topics range from philosophy:
"All we really know... I mean all we really know, is what we are told."
To the latest in medicine:
"It is the specific type of cheese that works, and the more organic the better! It cures muscle pain."
To current topics in health care and energy policy:
"We don't need nuclear power. If the government wants to solve the current obesity and energy crisis, they need to put the 100 million overweight lard-asses on treadmills hooked to generators, and dangle some bacon in front of them. The energy produced would more than suffice to power the needs of the rest of the US population."
Wait.... what... huh?
First of all, I ask the philosopher what kind of coffee he is drinking and how it tastes. "It's good... it is this special Colombian blend with a hint of vanillia."
"Did someone tell you it tastes good?" I ask, then move on.
"Tell me more about this cheese? Why not simply take aspirin?" I ask the medical student.
"Well. there are these specific enzymes that deaden pain receptors and reduce inflammation! It is all natural and it helped this Olympic skier win a gold medal. If it works for a world class athlete, then there must be something to it!"
"If an Olympic fencer said that trephination would relieve headaches, would you do that?" I ask, then move on.
"Hey, Mr. Bacon, " I interject to the energy/health guru/pundit and his cadre.
"Lets try some critical thinking and some math on your proposed solution to our energy crises."
I take a deep breath.
"100 million overweight people at 40 lb over weight (Using your numbers.) is roughly 4 billion lb. of fat. 3500 kcal of energy per lb of fat. That comes out to roughly 6e16 joules of energy.
America uses about 1.5e19 joules/year of electricity.
So if all the fat energy was magically converted to electricity, we could power the country for .004 years, or about 1 and a half days."
The pundits table falls silent.
Obviously they do not get the point, so I continue:
"Worse yet, the average human puts out 100 Watts of power day and night, and while exercising may get up to a max of 200 Watt for short periods of time. Try the math to figure out how much "treadmill" energy the entire overweight population can provide per day until they lose their excess baggage."
I shrug, bus my coffee cup, and head out into the real world, where the only people caught dead on a treadmill seems to be spandex clad models. (Or cute dogs).