How important is maintaining continuity for the time turners? If it IS important, then you can only end up with 6 you's (It's noon, go back to 11, pick up that you, go back to 10, pick up that you, etc...)
BUT! If your mission takes more than an hour, you will end up with a discontinuity, since then 6:00!you will not be back in time to be 7:00!you so that you's can pick him up.
If continuity is NOT important: Go back an hour. Now there are two of you's. Both you's wait around two hours, then both of you go back and pick up the past you's. Now there are four of you's. All four of you's wait around two hours, etc.... You'd end up with 64 you's (assuming you can animagus into a something really small to fit in the pouch that is)
Aaaaagh! Time travel makes my head hurt
Reality computes in one swoop. It simply wouldn't happen.
EDIT: New discussion thread here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With two chapters recently the previous thread has very quickly reached 500 comments. The latest chapter as of 17th March 2012 is Ch. 79.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author's Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight, nine, ten.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: