I found this hilarious Q & A buried in the archives of the Chicago Manual of Style online:
Q. About two spaces after a period. As a US Marine, I know that what’s right is right and you are wrong. I declare it once and for all aesthetically more appealing to have two spaces after a period. If you refuse to alter your bullheadedness, I will petition the commandant to allow me to take one Marine detail to conquer your organization and impose my rule. Thou shalt place two spaces after a period. Period. Semper Fidelis.
A. As a US Marine, you’re probably an expert at something, but I’m afraid it’s not this. Status quo.
I’m a diehard two-spacer. Abusus non tollit usum.