The pessimist in me says this is the regular old "If it's free, then you're the product" situation.

This seems like a clever way to collect valid mailing addresses. People are also likely to include personal information in their praise messages, which could be valuable data.

Their Terms and Conditions and Privacy Policy state they reserve the right to share collected information with service providers, business partners, and affiliates. They can use your data for "other purposes" including "data analysis" and "identifying trends." They can share your information with "business partners to offer you certain products, services or promotions."