I don't think it matters if you waive or not (to the evaluator).
That may be true for most - I don't know how you or I would know - but I'm doubtful you can really say "it doesn't matter" universally. To some it would, almost certainly, and to some it wouldn't. I'd feel more comfortable writing one if I knew my privacy was ensured, so it would matter to me.
I didn't really consider whether they cared or not; I didn't even ask them. I just waived it because I already knew basically what they'd write, I wanted to extend a gesture of trust to them, and in the end you can't see them until the game's over and you've won. According to VMCAS, you "still won't be able to see the evaluation until you are admitted and enrolled." [VMCAS Instructions, 2011]
So my take on it was: If I don't get in, I won't get to see what they wrote to find out if I misplaced my trust in one of them. If I do get in, I don't care what they wrote, good or bad. And on top of it, I trust them all. So... why not show them that?
@awaring1: I don't understand what you're saying, but I wasn't suggesting my choice was the only right one. If it makes you feel better to know that you can review your letters after getting accepted ... great. That's why the option is there, I 'spose.
After I didn't get in my first time, I did bring up the LORs in a review. She affirmed that she couldn't share them, but she did go so far as to say "they were all excellent, and you could use all of them again, but I'd make particularly sure that you use [so-n-so] again." I felt like that was a fair way to approach it.