> Do you have a good reason to believe that we can consider negligible the proportion of people who are entitled to participate in this class action but are not aware of its existence and their rights and responsibilities? Can you show that it's probable that they're not in the majority?

It's not really the set of people who are entitled to participate in this class action but are unaware of it that is relevant here. The relevant set is the subset of that group that would choose not to be in this settlement and also would individually sue Facebook over the legal issues and factual allegations involved in the class action.

I would expect that most people who are sufficiently concerned over the Facebook activities involved in this class action to actually individually sue would have already done so or at least started preparing to do so long ago and as part of that would have kept track of other lawsuits that overlapped with theirs.