The opinions about Santa Claus from those who never participated in Christmas, period, are interesting. I suppose, like most things, something relatively innocuous and joyful is seen as alien and wrong by someone who was denied the experience. You could discuss anything from Santa Claus to Oral Sex with the same experiential parameters and you'd find little changed about the conversation other than the subject. But I digress...
As someone who grew up with yearly visits from Santa, I can relay that in my own experience there was no giant sense of 'betrayal' at being *gasp* lied to. It was fun while it lasted, it was an interesting experience finding out that it was my parents who bought and gave those wonderful gifts, and is now quite fun for my husband and myself to take our turn at playing Santa. I don't even object to the disucssion Santa in class, but I do think that such discussions take care and diplomacy. My father, for instance, never actually 'lied' to us about Santa. He told me that Santa was a myth. As a very young child, I just assumed a myth was a fat guy in a red suit who lived to give kids gifts.
Our eight year old has been in the big questioning phase the two seasons now. He has friends that believe, and those that don't. When he tells us what his friends say, or he asks questions, my husband and I just ask him what he thinks about it. He responded to that question a few weeks ago by saying "Oh, I know there's a Santa, because last year I got a GameCube, and I know you guys couldn't afford THAT." I think this is our last true-believer Santa year with him, and I'll miss the joy that it has brought him--but he'll continue to get yearly presents from Santa, his toddler sister won't be his age for some time. And even then, I don't think Santa will ever go away. Heck, I'm 32 years old and I still get a present marked "From Santa" under my parent's tree every year.