
When I was rereading th 4th book (after the 5th; yeah, i know i'm not very coherent

I thought that DD must have seen in teenager Snape an ally, even before he could have joined to the Dark Side. Is it possible that DD has asked Snape to "join" Voldmort, but just to spy. In other word, could Snape have always been a good wizard?
He knows occlumency, so, Voldmort could have never found out that Snape was good. I've been checkin in Occlumency lessons (the part when Harry sees Snape's memories) and what Harry saw can't contradict my theory (although it can't prove it either).
We also know that Snape was in a group of Slytherins whose members fell into the Dark Side (it's Sirius who says it, I think, and in book 5), but no friend of Snape is with him at the end of his DADA OWL...
What do you think?
[And sorry for the looooooong post!!!]