Will the full installer for mountain lion disappear from the mac app store when mavericks is publicly released? That's what happened to lion when mountain lion was released. What if people want to downgrade back to mountain lion, or dual boot mavericks and mountain lion and clean install the partitions, but don't have bootable usbs of either? How are they going to download mountain lion if it is no longer available on the mac app store? Purchases tab in mac app store may solve the problem for some people who bought it before. But what about people who never bought it? Then it won't show up in purchases tab. Apple still sell redemption codes for lion if you call 1800MYAPPLE. But to get a download code for lion, you need to convince apple you have a mac which can be upgraded to lion, but not mountain lion. There are a few such computers. You can then redeem it in the mac app store. But I bet a lot of people who want to get lion will just download a torrent instead. But there are no such computers that can be upgraded to mountain lion but not mavericks. The supported hardware is exactly the same. So such special arrangements apple make for lion will not be made for mountain lion. How then to get a code for mountain lion? If they remove it from the mac app store, you will see more people downloading it from torrents. And that could be causing a whole lot of other problems in future too.