Oh, kids -- they're an attractive demographic, pretty good at making sneakers, AND an excellent stumbling block for most companies and their poor advertising campaigns.
Exhibit A: Target, and their Rounders campaign on Facebook
The Breakdown: Target gave freebies and large discounts to kids who promoted Target on the site and on the Facebook Group page. Members of the Rounder group were told to "keep it like a secret" from other users. One member felt this was wrong, wrote a paper for college, and her professor posted the info on her blog.
The Idiocy: The driving factor in word of mouth marketing is trust. Receivers have to believe that the source of information is trustworthy -- and not "ad-like" -- and blowback can be deadly. The damage from this type of outright deception can be much worse than simple negative feedback from a customer.
The Lesson: There are no well-kept "secrets" online -- especially in communities, especially regarding massive companies. Target, you were literally asking people to lie for you. People love Target, I know, I've tried going to Target and its always over-run with happy, smiling, excited customers. Asking customers to write about you is fine, but lying about why they're doing it ... that isn't acceptable on the social web, and this is just one more cautionary tale to prove it.
Besides, you're muddying the data. Feedback, whether its positive or negative, is valuable. By handing out cookies, and saying "say something nice about us," you're not taking advantage of the power of a simple conversation. Look, we're smarter than you think. When we see a page with nothing but celebratory comments, we know it's bullshit. But when we see honest feedback and engaged customer service reps, we see proof of a company that is customer oriented.