The Sony Walkman came out 45 years ago today. It would sell 200m units and ushered in age of personal consumer electronics (cellphone, iPod, iPhone). An interesting detail is that Akio Morita — Sony’s legendary boss at the time — thought it would be too “anti-social” and instructed his team to build the first Walkman with two headphone jacks. He was right about the anti-social aspect (people plugged in by themselves) but consumers clearly preferred the solo version.