I think GP's point is that the amount of the settlement is not enough given the total number of users involved, rather than the class action itself is insignificant.

In my opinion, in these type of cases, the amount should be directly correlated to how much revenue the company generated from the sale of the data. If the sale of my data is deemed illegal/unethical/etc, then I should reap all financial benefits plus damages.

What's stopping FB from just continuing this practice and just upping their costs to their customers to include this added "cost" of doing business?