You know you should do it, but you can't bear to see them disillusioned, to see the tears, the confused looks of abandonment. You're afraid to face that "Why, Daddy? Why?" moment. So, you don't do it. You don't tell them there's no Santa. You let them continue to believe in the Easter Bunny, the Tooth Fairy, the Pot-O-Gold at the end of the rainbow, Frankenberry and Count Chocula. You even let them continue to believe in God.
If you need a good reason to stop this nonsense, science is here for you. It won't stop the tears, but it will make you feel confident that you're doing the right thing. It's tough love, but there's a good reason for it. Check it out.