I never wanted to be a soccer mom and always told my children that their freedom ended where mine began because everyone's needs in a family had to be met. We also said no two years ago when a college with a $60K tag and no proposed contribution accepted our son. We've got to eat, too. And I said no to my daughter to Barbies (and not because we couldn't afford one...).
My parents set clear boundaries when it came to expenses. They said no when I learned to drive and had visions of grandeur, wanting a Triumph Spitfire - I got to share a car with my mom; they also said "we will only pay for one year, you've got to manage after that," when I decided I'd had enough of the Belgian university system and wanted to continue my studies in the US (and it was way less expensive then than it is now....).
Wednesday's NY Times article To raise better kids, say no explains that always saying yes "fosters a sense of deficiency that can never be fully satisfied," while learning to do with what you have fosters creativity, flexibility, resourcefulness, and inventiveness. It turns out that receiving some pushback teaches children to "solve problems more effectively."
Creativity, flexibility, resourcefulness, inventiveness, and good problem solving are are all qualities we most definitely need in today's complex world. So let's convey to our children that nobody's resources, most of all not our planet's, are infinite. Say no every one in a while, you'll do them a favor.