Continuity mistake: When Jake and Samantha are at the club, Anna messages Jake and the date on the phone is seen as May 28 at 1:25, however, when he gets the second message both messages are shown together and the date on the phone is December 1, 2010 at 11:58 am, and shortly after that the date on phone after the third message from Anna is received is May 28 at 1:31.
Continuity mistake: When Anna starts to open the balcony door in the hotel room she stubs her finger and Jake tends to her. The balcony door is only open slightly, with them standing in front of it. In the next shot the door is open about half way with both Anna and Jake standing on the other side of it.
Continuity mistake: At the beginning when Anna places the letter to Jacob under the car's windshield wiper for the second time, before walking away, only the bottom left corner of the note is under the wiper. In the next closeup shot the note is visible lower down under the wiper and closer to the end of the windshield at the passenger side.