What use is Snape in the rest of the plot?

[Ciji]

No: HPFGUIDX 133113

Hi, new here, thought I'd chime in...

Now, I'm no fan of Snape by any means, I'm still clinging to the hope
that Snape was bound by the 'unbreakable vow' to kill Dumbledore,
hoping mostly for Dumbledore's sake.  Remember how he hesitated before
making that last promise?  Keep in mind, the goal all along was to
kill Dumbleore, not Harry.  I'd like to hope that Dumbledore, the
greatest and most powerful wizard for the age and the only one that
Voldemort fears, was not so easily dispatched by Snape. I'd hate to
think that Dumbledore was done in by his own blind trust, rather than
in a great battle versus a powerful wizard.  

I also have come to realize why Sirius had to die in OotP.  Sirius was
to only person who truly saw and accepted who Snape really was. 
Despite Dumbledore's trust, Sirius never bought Snape's act. Had
Sirius been alive, he would have completely sided with Harry and done
everything in his power to stop Snape.  Finally, I can accept that
Sirius had to die, because if he hadn't, HBP would be a very different
book.

I also agree with whomever said that there is no way Snape can survive
book 7.  He's pledged alliegance to 2 sides-- Voldemort and
Dumbledore, and breaking a promise always has consequnces.  And how do
we know Snape didn't make some type of vow to Dumbledore, something
along the lines of "in the event of your death, I , Severus Snape,
promise to..."  No doubt Snape will play a MAJOR role in book 7. I
hope Harry kills him... with pain.

What is also interesting is how accomplished an Occulemens/Legimens
Snape is, and how poor at both tasks Dumbledore seems (seemed) to be.
 Tho' I didn't fully trust Snape, who knew he was that dang good!  I
guess when you have no friends in high school, you have a lot of time
on your hands...

Lastly, it would be great to think that Dumbledore took precautions
'just in case' he died to return to life, like a pheonix, but that
would mean he'd need a horcrux, right?  But like someone posted
earlier, Dumbledore thought he had plently of time to get his affairs
in order, so to speak.  And Dumbledore doesn't strike me as someone
who'd try to 'cheat' death or live past his time.  At best, we can
hope Dumbledore's essence is in a painting on a wall at Hogwarts.  At
worst, we can expect he is gone for good. 

"Ciji"