While I have a pseudonymous fakebook account, due to it's age (I couldn't make one now, I think), I don't use it anymore.

The vast network of data really gets around pseudonymity anyway, because they can link various databases, and completely profile you even if you don't post on social media.

They can get your personal details through means other than you posting. Other's posts, texts, etc... While you can reduce the details you provide, most salient details, including views on matters they deem important, are still able to be collected about you from other sources.