My 6yo recently decided our family is poor because the 7yo next-door neighbor got an ipad for his birthday. When my 6yo, who gets to use my ipad as much as I would allow her to use one of her own (and there is never conflict, because I rarely use it for anything, anyway), asked me if SHE could have one for her birthday, I said that is too expensive. I didn't get into the details, really that is too expensive for the minimal value it would have to her. It is too expensive a toy to allow her to play with it in the driveway with neighbors on bikes whizzing past, as neighbor child was allowed. Truly, my children want for nothing and have most of their heart's desires...but I would not let either of them own an ipad. My 10yo stepson, sure.
Anyway, I agree with others about the concept of ownership. I am very careful to make consistent and fair rules about sharing and ownership. Both of my children at 3 would have understood the concept of an item they own but have limited access to, no issue. But while both of my children were and are very sweet to willingly share all their belongings with their parents and everyone else, they would expect and deserve to be asked before borrowing an item that is theirs. If that isn't the situation I wanted with an electronic devise, I would not allow it to be gifted exclusively to one of my children.
I still remember times when adults disrespected me by assuming my rights of ownership were less because I was a small child. I think saying that something belongs to a child but has to be shared whenever the grownup wants to use it is only fair if the same thing holds true in reverse. Which I can't imagine being the case.
Look, if I want to cut a piece of paper and my 6yo is using her scissors, I need to ask her to borrow them and acknowledge her superior claim to those scissors. Just as if she wants to type on my computer, she has to ask and acknowledge my superior claim to that computer if I am already reading an article or something. This is not the same as being over-ruled due to practical concerns.