Using your argument I guess I would be at fault for allowing my child the imagination she has and especially for playing along with her as she is being chased by a lion or becomes one herself and chases me.
Two things.
1. Computer programmers tap into a lie that has been told several times over and create a realistic video using personal information supplied by the parent. The video suggests the child is being watched and if they behave they will receive gifts. This is not based on imagination because the child isn't not imagining anything - at the very core the whole thing depends on the child thinking it is real.
2. A child using their own imagination creates and pretends a story. She decides on characters and a series of events and controls and participates in the action. She knows it is pretend.
These are entirely distinct processes. Outside of the Santa context if you heard of a parent hiring computer programmers, paying for television air time, hiring people to hang around the mall all to tell their children something that wasn't true presumably you'd at least find this odd if not possibly a bit abusive.
As I said before this is one of those YMMV things. People don't all react in the same way for sure. There are lot of variables concerning the individual personality of the child and also I'm sure the way in which they find out and if parents are invested in pushing the manipulation. Given the tendency of many gifted children to be concerned about issues of respect and justice it may be worth considering the long range implications.
