Is clearly that Mr. Robot is Elliot imagination. The fact that Mr.R speak loud and in that manner in AllSafe without any of the employees there to warn him about his behave it confirms what I suspected from the previous episode. More, no one could had enter random in such company dress like that and sit on Elliot chair waiting for him, the same clothes which his wearing from the first episode, same cap too. The employee that was next to Elliot desk, the girl, raised his head for a moment because of Elliot talking *alone*. Another one is the bar scene like everybody said, no eye contact there from the bartender to Mr. Robot and in the first episode, if I recall, when Elliot meets the Fsociety in the garage, no one, again made any eye contact with Mr. Robot or speak to him, however there is one thing that intrigues me is when the videoclip with the masked person was actually Christian Slater, his voice, but I do wonder what if that was actually Elliot masked with altered voice. Might Elliot be the one who is losing memories and living on two lives he created because it seems that Fsociety are waiting for him, the actual leader.
I'm guessing that Mr.R could be his father and Elliot forgot how his dad looked like when he was young.