Character mistake: About 3/4 of the way through the movie, when Jennifer Aniston is talking to Ben Affleck, she calls him Ben instead of his character's name Neil.
Visible crew/equipment: In the first half of the movie, when Jennifer Aniston tells Ben Affleck her sister's getting married, a cameraman's reflection appears in a painting on Ben's left. It happens again a few seconds later.
Continuity mistake: When Gigi calls Alex for the first time to get his opinion about a guy "Jarrad", Alex puts her on hold and goes into his office to pick up the call. In the bar the phone line is lit up where it's holding, but the office phone is not lit up at all.
Deliberate mistake: When Janine smashes the mirror she takes it directly off the wall and raises it above her head, and the reflective side would be facing behind her. The camera immediately cuts to a front view as she's throwing it down and the reflective side is in front. This was probably done for dramatic effect so that the reflective side would hit the ground first.
Factual error: When Ben goes to Anna's yoga class, we see the very end of the class. Everyone is seated upright, cross-legged. In real life, yoga classes always end in savasanah, a pose where you lie on your back and breathe to take in all that the body/mind just did. They just had the actors seated upright to show them making eyes at each other.
