Yoplait, et al and their 'philanthropic' promotions
If Yoplait is so interested in funding research for breast cancer, why do I have to send in the lid from my yogurt? If you want to impress me just donate the money - a nickel for every tub sold or whatever. Tell me about it all you want. You can have the same huge ad campaign, print the same self-congratulatory slogans on your lids, and have the same or greater impact on cancer research.
If you want to generate some mail you could even ask your customers to match your contributions. I'd be more inclined to do that than to send you back the lid from my yogurt. Yuck.