The 300,000 apps that are 'missing' have been forcibly removed or have been replaced by newer versions over the last four years.
Apple's closest competitor, Google, announced on November 1 that its Google Play Store had passed the 700,000-app mark, however, it turns out that six of them were actually fake Apple apps, pretending to be GarageBand, iPhoto, iMove, Keynote, Numbers and Pages. They were discovered on November 18 and promptly removed from the store, but not before a number of Android users had paid between $4.95 and $9.97 to buy them.