How on earth is this possible; this guy just goes to gmail via google.com and BOOM! suddenly he is logged on to SOMEONE ELSES GMAIL ACCOUNT.
He's not a hacker, just an ordinary lad, who is "a bit" confused by all this. He is actually concerned of this obvious security problem and as he gets logged on to people accounts he sends an email to the person from the persons own gmail account. He is telling them that who he is and tells them that they should change their password.
In this video clip, Richard is asking for all of the gmail-users/youtubers to describe their experiences if they have encountered the same:
http://www.youtube.com/watch?v=IEWThr_2h0Y