> I've failed to see why concerns over Facebook handling your private data is worrying when they don't have a product you need to have.

I have at least two concerns.

1) Viscerally, it would be intensely creepy if someone started following me everywhere. Why would I want a company doing the same?

2) We are in an era of diminishing freedoms, and it's impossible to prove that data Facebook has on us can't be turned against us in the court system in the future. Women's menstrual cycles are being weaponized, for Pete's sake.