Whys is Snape allowed to continue spying?

[rosered2318]

No: HPFGUIDX 131533

My personal theory is that Snape is a spy, but not THE spy.  I think 
Snape is a red herring for both the DE and the OOtP.  My money is the 
Rookwood is actually THE spy for the Order, and someone yet to be 
discovered is spying on the Order for Voldemort.  I read a great essay 
at the Lexicon about where all the DE's were during the fight at the 
MoM and Rookwood appears to be absent throughout most of the 
fighting.  He reappears in the Death Chamber (or whatever it is 
called) at the end, fighting Kingsley with another Death Eater at his 
side.  The next thing we know, Kingsley is fighting just the one Death 
Eater.  Rookwood got out of the battle pretty quick.  Take into 
account that Bagman was found passing information to him and Bagman 
managed to get released....maybe Bagman truly is an idiot and Rookwood 
let someone know it was unintentional.  

Come to think of it, how did Snape get away with not being there?  And 
wouldn't he have known that there was going to be a trap?  It appeared 
as though ALL the DE in Voldemorts inner circle were at the MoM.  I 
was under the assumption that Snape was in the graveyard in GoF....(if 
you respond do this, please change the title so it doesn't get messy)

Rosered