The blood stain on the back of Elena's top is considerably smaller this episode than it was last episode.
When Bonnie is preparing to send Elena a message she tears a page out of her notebook, closes the note book and starts to write the message, then the camera angle changes so you can see what Bonnie is writing and her notebook is open and she is writing on a page that hasn't been torn out of it.
When Rose back hands Elena, she falls with her lower body in the floor and her upper body bent over onto the sofa face down. When the camera angle changes, she is lying on her side with her whole body (except her legs) on the sofa and her head resting on the arm of the sofa.
While Jeremy is placing the map on the table, Bonnie tells him that since he and Elena are blood related the connection should be stronger. Elena is adopted and so people incorrectly assume that she is not related to Jeremy, however Elena's biological father is John Gilbert, Jeremy's biological uncle, thus making Elena and Jeremy biological cousins and therefore related.
When Elijah grabs Elena's necklace and chucks it to the ground he should have noticed that it was his Mother's necklace as it is rather unique.
In Season 2, Episode 8, Bonnie uses her locator spell to find Elena. She asks to use Jeremy's blood saying that since they are blood-related, the connection would be stronger; however, it was earlier revealed in the series that Elena was adopted. Therefore, her and Jeremy are not blood-related siblings.