The carrot is the in-game currency. Who do you think will write the most reviews, reflecting the average score; people who want in-game currency or people who will never play the game again? edit: The details are prominently placed in the middle of the screen when you click the link, but in case you couldn't find it... 20 diamonds for a review (if you send in a screenshot of the review) and 10 more for a 100+ word review, no "positive" requirement for payout.