Average Speed = Distance * Donuts Eaten

Donuts are good.

But I still say we should standardize on Googles. That is, how long Google Maps expects over how long it takes us. Say, Google says my commute is 42 minutes and I do it in 24, my average speed would be 1.75 Googles.

I'm highly disappointed by Google's calculation of cycling trip time. It quotes down at like 12mph with no regard to traffic or climbs etc. They need to raise the bar and improve resolution to include minutia in their calculations; else what's the point of Google even providing such a service.

Yes, that was what I was trying to convey, though not as clearly as I intended. The phrase "simple logic" or the word "most" should not have been used. What I meant by "simple logic" was the faulty logic that if I rode half the distance at 10 mph and the other half at 20 mph, that the two distances would have equal weight and the average should be the median of 15 mph. As you pointed out, the correct logic would be that only the total distance and total time are relevant and you rode at 10 mph for 2/3 of the total time thus having a greater effect on the average speed. I didn't expect that any bike computers would use faulty logic to come up with 15 mph in the example, but it would be easy for someone to use the "simple" but inaccurate method to come up with 15 mph and then be discouraged when their computer revealed the correct 13.3 mph.

This can be disheartening when you have had a great average speed over a relatively long ride only to have the life sucked out of that average by hitting a steep grade, strong headwind, or a bonk during just a few miles at the end.

With Google who knows, but I have the impression that they do consider elevation changes and lights at least. When I check a local road, North Point Pkwy for example, it's slower uphill than downhill.

I'd like to see them take into account traffic, like they do with driving time, and also weather. And then scale it to the individual. They have the data - Google has a better idea of where I've been, and how long it took, than I do.