Evil Snape? I think not.

[tinksterl]

No: HPFGUIDX 133179

 
> It just doesn't add up to Snape being evil, although I am afraid 
> Snape may have to pay for a crime he committed out of duty. He 
will 
> have no ally in the order due to Harry's witnessing of 
Dumbledore's 
> death, unless dumbledore himself (in painting form perhaps) 
explains 
> the situation to someone else. 
> 
> Hanna Delacour

We also learned a possibly important lesson in this book - memories 
can be contained, and stored indefinitely, to be perused later, even 
after the person they belong to is gone.  As much a fan as 
Dumbledore was of using the Pensieve, I wouldn't be surprised if, 
in the case that there was indeed an agreement between himself and 
Snape, there is a vial he left tucked away somewhere.  After all 
their "lessons" this year, Harry would surely recognize it for what 
it is (a memory) if he sees it.

-Tinkster