Here's an easy explanation.
Someone you don't like somehow gets voted into power and begins trying to enact changes towards a social group you belong to.
Building anonymous systems is one way to avoid Bad Actor X from having Big List Y, leading to Atrocity Z.
Having a really successful social network isn't a goal post, it's just a result.
Great -- it made a zillion dollars, meanwhile we've built the biggest leakiest information trove on individuals, for individuals to be exploited, ever imagined.