The conversation between Derek and Melanie about the Dave Matthews Band wasn't in the original script.
Around the 1 hour mark, when Melanie (Samara Weaving) takes off her top, she reveals a Metal shirt by the Death Metal band The Black Dahlia Murder, with the cover art from the Nocturnal album. Director Joe Lynch is a fan of Heavy Metal, which is audible and visible in most of his movies.
At one point when there is a close up on Derek, the blood on his forehead spells ID. Clearly a reference for the fact that the ID-7 virus causes you to be driven by pure id.
The office building this film was shot inside of only had three floors.