This is what I was thinking about while I was installing a bottom bracket tonight:
How do you manage to get twelve 1/4" bearing balls into a bottom bracket cup so you can remove one and have eleven balls in the cup? Twelve balls won't fit. Eleven is the correct number and that's how many fits. It doesn't work for hubs, either. It irks me every time I read that advice on here. Do people follow it because they believe everything they read on the internet is true? Maybe they think that people wouldn't be giving advice if they didn't know what they're talking about.
Yeah, I've had trouble buying that theory too. I think the point is to make sure there is space for the balls to shift side-to-side so they aren't rubbing against one another too hard. It really wouldn't hurt to use 10 balls where 11 fit comfortably, but its bad to use 12 if they just barely fit.