Social media - starting with the very early ones: Six Degrees, Friendster, maybe MySpace? - weakened that expectation, but (someone tell me if this is accurate) my recollection is that Facebook was the first platform to require realname accounts. I agree with you about the current danger, and though I've never posted anything anywhere that I wouldn't stand behind - trolling just isn't my style - I have, reflecting the pov of my "internet generation", always felt super weird publicly posting anything under my real name.