Apple has said that the next iteration of its OS X operating system will be sold exclusively through the online Mac App Store. This means you will require a fast Internet connection and an Apple ID in order to upgrade to this OS when it releases later this year.
Apple started this trend with Lion, which was its first OS to be sold online. They even removed the software DVDs that were provided along with Macs that were sold with Lion pre-installed. However, later on Apple did start selling the OS on bootable flash drives through its stores for $69, which is a lot more than the $29 you pay for the OS through the Mac App Store. However, that option will be discontinued with the release of Mountain Lion.
Having said that, it’s not as bad as it sounds. You can easily create a bootable USB flash drive on your own after downloading the OS from the MAS. You will find plenty of tutorials online that show you how to do it. Hopefully, the process will work with Mountain Lion as well.