Apple just announced that 100 million apps have been downloaded from the Mac App Store, in little less than a year of operation — it launched on January 6th and sold a million apps in just 24 hours, as well as a million copies of Lion in just a single day. It's impressive growth but still basically spare change next to the iOS App Store, which hit 100 million apps downloaded in just under two months of operation and now moves a billion apps a month with some 18 billion total apps downloaded. Even still, we're sure Apple's quite happy running two successful app stores — and quite happy to set a high bar for Microsoft to hit when it launches the Windows Store next February.