Transmitting messages between users is a functional property of Mastodon that is of course visible and valuable to the users. Transmitting protected health data from Flo users to anyone with a dollar to buy some ads is not a functional property of Flo itself or a mobile ad product, and likely surprising to both Flo and Flo's users. Facebook has discretion on how they use that data. If this is a rare and unavoidable consequence of their business model Facebook should be comfortable paying the settlements as judgements occur.