Re: Mood at F8?
I'd say the developers were enthusiastic about Facebook's renewed statement of commitment. Zuckerberg end announced next year's F8, to reassure developers that Facebook is serious. Now keep in mind that Facebook's announcements were aimed to make Facebook development tech more appealing for people making apps. Anonymous login isn't about Facebook giving up on personal information; it's about helping people trust apps with FB Login enough to try them (so they can then later provide personal information).
If Facebook can translate its vast reach into must-have services, it will redefine what it means to be cross-platform. Yesterday's platforms didn't require a data layer. Apple's policies were aimed at protecting paid app sales. Tomorrow's platforms will rely much more heavily on a data layer, from Facebook or someone else, because advertising, engagement, and other marketing data will become so much more important to make free apps profitable.