Showboating, I've always assumed. A good deal of the questioning was clearly grandstanding, and a good number of the questions asked could have been answered by the Senators' grandchildren.
That said, if you want to grandstand, you should first run your questions by your grandchildren so they can tell you about online advertising and such, lest you look like a fool on national television.
I have known techies voicing issues and asking questions about Facebook practices wayback in 2008-9. You can say it took 10 years for the rest of the population to start asking the same questions. But I see it as a failure of the early warning technical crowd, who knew bad things were unfolding, to warn us faster.
Whats the lesson there?
(Disclosure — I am a Fitbit engineer.)
This seems like a very legitimate question. He wants to know if Facebook tracks e.g. your FitBit. It's connected to your phone, and your phone is connected to Facebook, but your FitBit isn't connected to Facebook. And to be honest, I don't know the answer to that question. I would hope that they can't, but knowing the state of the tech world (IoT: the 'S' stands for security), it's probably possible, and knowing what we know about Facebook, if it's possible they are probably doing it.
Not that Zuckerberg would necessarily know or confess to it before the Senate, but that's a separate issue (I often wonder what is the point of calling a corporate executive to DC anyway, since they have every reason to dissemble and no reason to cooperate in good faith).