The basic idea that incentives can be used to motivate behavior is a powerful one. It works for employees, and it has a clear place in parenting, as anyone who has tried to potty-train a recalcitrant toddler with sticker rewards knows.
A friend is like a good bra: hard to find, comfortable, supportive, always lifts you up, makes you look better, never lets you down or leaves you hanging, and always close to your heart.