I was working on a project in school once where (almost) everyone forgot the scale that we were using. So I was working in cm units which I equated to one foot. others were working at a scale I have yet to figure out, 1 maya unit equals .4 feet. Then others were eyeballed. To make things worse, some students prefs were set so that the default units were inches instead of centimeters and they didn't know. It was a huge mess.
And to make things worse, sometimes the grid display would magicly change so I thought that I was working in the right scale and I wasn't(the grid would display in cm units while the scene units would be in inches). I ended up having to create a sphere with a radius of 1 with all of the settings perfect and then import that into each scene to make sure things were correct by comparison.
AND the character had been rigged at a scale that didn't match anything else. I came close to going to anger management classes after this.
I don't think anything else could have gone wrong.
My background is is architecture so I am a little fanatical about scale, especially on a set or something where the values can be easily adjusted so that they are perfect, or at least exactly what they should be for the design.
I hate you European guys/gals with your simple metric system and it's logic and ease of use. No, wait, I hate the fact that in the US we have teachers and a general public that will not adopt a logical system. It get's so old trying to convert measurments like 4 feet 5 and 7/8 inches inches to anything. Even converting 5/8 of an inch to .625 gets old.
Sorry for the rant/story. Scale is just near and dear to my heart.