I am Mountain Lion 10.8.5. This is a common problem, but couldn't find any answers specific to Mountain Lion or my exact problem. I wanted to see folder sizes in Finder, which is turned off by default. I went into "Show View Options" and then checked "Calculate All Sizes". I then click on "Use as Defaults" button, which goes from black to gray when I click it. I would assume "Use As Defaults" would apply for the entire hard drive. But it seems to be applied randomly. Some folders have sizes, some don't. Sometimes folders will not have the size shown but subfolders will. Any ideas?