Donation packaging

I went grocery shopping last weekend and noticed special advertisements I had never really paid attention to before. So many items whether its clothes, food or even hair products have are connecting their brands and even donating some of the profit to certain organizations. For example, Yoplait yogurt is has breast cancer ribbons on their tops so every time you buy Yo-plait yogurt you are donating a certain amount to breast cancer research. Another example is Chegg.com, the popular book rental website for college students, plants a tree somewhere in the world each time you place an order with them.    Do you think this is an effective way of advertising? If you saw this on a product you were buying, would you be more willing to buy the one donating or the generic brand?