My half-sister Milly is 3 1/2. She is probably the cutest thing on the planet and is possibly aware of her power. She has curly hair, a heart-shaped face, enormous eyes and when not dancing in the style of her favourite R&B bands - she's a far better dancer than I ever could be, she has a tendancy of running up to and launching herself at people, opening her eyes to their widest extent and exclaiming "I wuv you" with all the sincerity she can muster. When you've got used to this, and learned to turn so you don't get headbutted in the nads, you notice that she only does this to people who do stuff for her. Milly never once tried the IWY trick on Paula who is less happy around children and didn't really do anything for Milly. Paula doesn't mind my Dad's new family and actually likes simonjrogers', possibly because they don't try to climb all over her, and because she knows them a bit better.
So after having read several Angelina Ballerina stories, during which Milly is very attentive and quiet, or played "this is the way the farmer rides" - the fell of his horse variant, I started to wonder whether the IWY was a genuine expression of innocent sentiment, some reward for having entertained Milly, or perhaps an enticement to entertain her. The fact that Milly never did this to Paula, or anyone else whilst I was there, suggests one of the latter, although she might be aware of Paula's need for personal space, or at least her less welcoming attitude.
I'm not suggesting that Milly is mercenary, I'm not sure she's that aware, but she has learned positive reinforcement and that's probably a good thing.