Don't tell a kid there are no limits to his or her desires. First, it's wrong. There are simply some things he or she cannot do, either because of innate gifting (or lack thereof), opportunity, or legality. Second, it will breed a sullen thanklessness. After all, if there are no limits, then I am entitled to whatever I want.
Teaching children about limits will, counterintuitively, encourage thankfulness when they do get what they desire. It will also keep them from constantly asking for stuff (particularly when you are on a hurried shopping trip). So go ahead, parents. Love your kids today. Just say No.