Well, whatever gets Facebook to take privacy seriously, I'm all for it. It remains to be seen how this 'new Zuck' will change FB internal processes - which we probably won't know for quite some time. Until stuff like this stops happening regularly, it's all just talk.
As to the heart of the matter - there is merit to what he said. Facebook was created for sharing personal stuff, and that inevitably works better if audience isn't the whole wide world, and there for all eternity, indexable and searchable. That is opposed to Cake, which is here for people to talk about their interests, something for which you naturally want to widest audience possible.
There is place for both, I think.