I signed up, couldn't figure out how to unfollow the people they'd assigned me to or un-recommend a book I'd clicked on by mistake.
Went looking for a way to give feedback. Found their "make a suggestion" forum, which is the only way to give feedback... there is no "contact us" button.
Found
the most egregious rights-grab I've ever seen in a TOS, including not only the right to make derivative commercial use of anything you submit to them, but "UserVoice may share as it sees fit information that you voluntarily make public, including information that you post on any blogs, message boards, chat rooms or other similar forums, whether or not such forums are owned by UserVoice."
My blog post got a response from a staff member, who said that UserVoice just manages the forums, not Riffle itself. I pointed out that, with no TOS available on Riffle, I have no way to know that.