"DeckEpic would like to access your public profile, friend list, email address, News Feed, birthday, work history, education history, hometown, interests, current city, religious and political views, personal description, likes and your friends' work histories, education histories, hometowns, interests, current cities, religious and political views, personal descriptions and likes."
Eesh. I understand why it's asking for this data, but I can't help but feel that that DeckEpic may be mining for more nefarious purposes.
The NY Times does this to some extent. Comments are moderated in batches. Comments within the first batch are about the article itself. Subsequent comments are made both on the article and in response to thoughtful comments that made it past the initial moderation filter.
GMail generates revenue, so it doesn't work in your example as a "free" service. You pay for it by agreeing to have your email trawled to pull relevant ads.