Huge clue to Snape's true allegence hidden in OotP?

[Diana]

No: HPFGUIDX 144707

I'm currently re-reading OotP and something in the "Occlumency" 
chapter jumped out at me.

Snape is explaining to Harry why DD want's him to learn Occluemency 
and Snape says (words emphasizd by me):

"The Dark Lord, for instance, *almost* always knows when somebody is 
lying to him.  *Only those skilled* at Occlumency are able to *shut 
down those feelings and memories* that contradict the lie, and so 
*can utter falsehoods in his prescence* without detection."

Re-reading that paragraph now after knowing the events in HBP, it 
occurs to me that Snape can only be speaking of his personal 
experience while telling Harry this.  Why?  Obvisouly Snape would 
know that the lies he's told Voldemort haven't been detected because 
he's still alive and is allowed to go in and out of Voldemort's 
presence without restriction.  

So, if Snape is capable of repeatedly telling undetectable lies to 
Voldemort does that pretty much mean he's on the side of the good?  
Or does it only mean that Snape is more than skilled enough to play 
both sides against the other while looking out for himself the 
entire time with the intention of choosing the winning side in the 
end?  

More to ponder in the mystery that is Snape's true allegiance....

Diana L.
dianasdolls