Thanks for the feedback and glad you liked it so far!
The donate a book campaign is our way of encouraging users to share our app. Instead of spending $ on facebook ads, we figured we'd donate a book every time 2 of your friends download Zolt using your referral code.
The Shout feature is meant to give users another way to express themselves (in addition to the usual share on FB, Twitter etc). It's still a work in progress, admittedly.
Thanks again though for the caution - will be careful of avoiding feature creep.
