Thoughts on this guy's approach?
[VIDEO]http://www.youtube.com/watch?v=MuzB2_O8GGM]YouTube - ‪Learn the notes on the guitar fretboard. Part 1 of 3‬‏[/VIDEO]
Even after all these years, I still couldn't immediately tell you what note you're playing if you just picked up a guitar, fretted something around 15 or so and said "What's this?" - it'd take me a second or two to do the fret-math, and the way I approach it is kind of like this guy's method. I find the closest note that I know, and then add/subtract, so to speak. However if I'm playing, 99/100 times I'm usually dead on if I know the key changes. (20 years of it will do that, I suppose)
This seems like a pretty neat way to go about it.
My guess is he played piano.
I always did the fret math when necessary but I memorized the hard way. Half the time it isn't needed though. In most cases I had to complicate things with fret numbers from working with guitarists for whom key signatures had no meaning.