revisiting the snape question...

[saturn]

I'm working on what we can loosely call a research project and I'm seeking alternate opinions & viewpoints. In a nutshell, I'm interested to know who you think Snape is fighting for and, more than that, what pieces of canon led you to your belief. Extra house points if you help me out by pimping this elsewhere.

[Poll #836251]

What in canon, if anything, supports your assessment?

Assume spoilers through book 6 in comments.