After the power was turned off to attract the creature to the van, it drives through the downtown area with all the city lights on.
The countdown clock, which can often be seen in the background, shows different amounts of time again and again, meaning: At later points in the movie it shows that more (!) time of the countdown is left than in scenes before.
The arch is eaten by the black hole. Later in the movie, the arch is seen in the background.
As the lab is collapsing, a school bus that wasn't there as the helicopter takes off suddenly appears in the next shot.
As Eric is driving to meet his ex-wife and daughter, he and the steering wheel are on the wrong (passenger) side of the van. When they show the van from the outside, turning a corner, he's back on the driver's side.
A strange matter 'black hole' formed in a particle accelerator would sink down into the center of the planet rather than travel along the surface as depicted.
Marines do NOT wear their ribbons, shooting badges and dress Eagle, Globe and Anchor in their BDUs.
At 44:06, Ryker refers to General Tate as Lieutenant General. even though he wears four stars on his uniform. Lieutenant Generals only wear three stars. The General also wears one large star on his cap, which is also incorrect.
A little after the collapse of the Midwestern Quantum Research Laboratory, Gen. Ryker reaches Town Hall. At that time, Director Hayes is watching a news report while having a conversation with his secretary (about 44:10). The female newsreader starts, "Another update; sources at both the Pentagon and the Department of Homeland Security are now officially describing this dark mass we're seeing just outside the downtown are of St. Louis as a black hole." Hayes' secretary informs him about Gen. Ryker reaching the new command center. At this time, the audio for the news flash finishes and then can be heard starting once again with "Another update; sources at both the..."; an obvious indication of a prerecorded segment that was timed and set to loop while the scene was filmed.
Though the alarm in the lab is going off and a voice on the intercom instructs all personnel to evacuate immediately, when Sgt. Bennett is sent to search for a missing person, three people in red shirts can be seen idly standing around in an overhead shot.
When Eric is moving the Hummer closer to the electric alien, the whole set is reflected on the truck when it passes the camera.
The Soldiers Memorial is on a direct path between the McDonnell Planetarium and downtown St. Louis and would be eaten by the 'black hole' before it got to the stadium, Old Courthouse, and Gateway Arch which were also shown as destroyed.
At approx. 32:00 minutes into the film a shot of a crowded freeway is shown during the evacuation of St. Louis. Even though the video is blurred for effect, an overhead freeway sign can be seen on the right side of the screen indicating the I-405. There is no 405 freeway in St. Louis, MO.