The character played by Emma Watson, while seen holding a cigarette and putting it to her lips, is quite obviously not inhaling said cigarette, revealing that she isn't actually smoking.
(At around 35 mins) Rebecca and Marc are driving listening the "All of the Lights" by Kanye West. This song was released in 2010 despite the film taking place in 2008-2009.
As Nicki is being shoved into the police car, a camera shadow is briefly visible on the arresting officer.
(Around 52 mins) The cameraman is vaguely reflected in one of the girls' sunglasses as the group walks down the sidewalk - before the scene where they return to rob Hilton's house a second time.
As Marc is being driven home by his mother, the camera's matte box is reflected on the car window.
The map online, you see "7764 Torrey Pines Circle Los Angeles, CA 90059". The 7764 Torrey Pines Circle is Anaheim, CA 92807, not Los Angeles, CA 90059. And the pictures of the map are different.
(at around 1h 10 mins) Nicki refers to her younger sister Emily, as "Gabby". The names of all the participants in the Bling Ring were changed for the film, but Gabby Neiers is the real person the character of Emily was based upon.