From Snape's POV, Harry's camp is Dumbledore's camp - to be around Harry he'd have to keep on being a Professor at Hogwarts, and Dumbledore will make sure he's his piece if he's on his home turf. Harry won't have his own proper camp for years yet, not something he could defend against Voldermort-level opponents by his and his allies' own magic power.
There's another reason: (edit: as far as Snape knows...) Harry doesn't know Snape was a Death Eater, a double agent, and the one responsible for delivering the prophecy to Voldemort! If Snape moves openly to support Harry where this doesn't mean supporting Dumbledore, then Dumbledore will warn Harry against him by revealing Snape's past, and Harry won't ever trust Snape after that. The impression Snape created in his last private conversation with Harry was bad enough.
Even if Snape merely tries to approach Harry privately, Harry will want to ask him questions about the last war. How did his parents die? What does the prophecy say? How did Dumbledore manage the last war? He'll be asking because Snape was there, but true answers will cast Snape in a very bad light.
Sure, on the gross level it's just swapping out "tied to Dumbledore's faction because that's where he can watch over his lost love's son" to "tied to Dumbledore's faction because that's where he can watch over someone who might be in his own long-term rational self-interest to support."
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: