The way Apple handles preorders depends on a couple of things: how much stock they have and how in-demand they think their latest gadget will be. For example, when the third-gen iPad debuted in March of this year, Apple started taking preorders almost immediately, but last year, when they debuted the iPhone 4S, they waited for three days until midnight PST on Friday before taking preorders.
It’s easy to see why. Even though there were enough third-gen iPads to go around, preordering the iPad was madness, and brought Apple’s server to its knees. By starting preorders in the middle of the night, Apple can mitigate server load, since most people won’t wake up in the middle of the night to get a new phone.
No surprise, then, that it’s looking increasingly likely that Apple will follow the same strategy this year, with the iPhone 5 not becoming available for preorder until Friday, September 14th at 12:00AM PST.