Visible crew/equipment: When Hal goes outside after his special "seminar" in the elevator with Tony Robbins, he hails a taxi and walks over to open the door when he notices that a woman is also opening the door. As the shot pans back from the taxi and he is apologizing to her, you can clearly see a boom microphone reflected in the triangular window, moving back and forth. (00:17:00)
Visible crew/equipment: When Tony Robbins slams the limo door to confront Jason Alexander, a crew member can be seen in the door's reflection.
Visible crew/equipment: When in the elevator, Tony says "OK, hypothetical situation..." and as he talks, to the right of the screen you can see some equipment moving around. (00:14:25)
Visible crew/equipment: When Jack Black and Jason Alexander are in the gym, Alexander talks about cankles. Watch the upper left hand part of the screen. The boom mic dips into the shot at least twice.
Answer: I think he was in the movie to reinforce that she is a genuinely nice person and that she had a wide circle of friends who appreciated her.