Big Brother is an all-seeing, all-knowing, totalitarian leader of a society that wields its power for its own sake, using surveillance as a tool towards that end. That's what some massive corporations effectively are today. People think today's Big Brothers are benign because their mission statements seem just or useful, but as I've shown above, there is significant potential for collateral damage.

You're right, and we've needed to control those means numerous times over the millennia. Sometimes just to keep the powerful in power, sometimes to check the powerful, and sometimes to check the surging wave of popular revolt.