Stupidity: When Flint Marko is escaping from the police, he climbs a chain link fence into a test facility. Besides having a chain link fence, there should have also been security cameras around the area as well as guards to prevent anyone from trying to get in. Plus, when the scientist notice on their computers that there's an increase in mass, one of them simply assumes it's a bird and then they continue their experiment. Instead of making assumptions, they should have halted their experiment and have someone take a look to see what caused the increase of mass.
Stupidity: (SPOILERS) Despite knowing that Rowena killed the last person who was blackmailing her, Miles tries to use her secret to blackmail her into sleeping with him. Did he really believe that she wouldn't react with such drastic measures like she did before?
Stupidity: When Stuntman Mike is taking photos of the girls, he is shooting with the lens cap on the camera.
Stupidity: When Michael goes to Judith's room, all she says is, "Michael, what are you doing in here?" She doesn't even ask why he's all bloody.
Suggested correction: It's Halloween, and she most likely thinks he's got into the spirit. Let's also not forget how she treated him earlier when she blew off taking him trick or treating. It's obvious she doesn't care about him at all and is beyond self centered so it's not surprising she wouldn't comment on it.
Stupidity: Kale screams for Ronnie after he sees the image of the club girl on the videotape, and Ronnie proceeds to just stand there and doesn't even bother to go up to Kale to see what is wrong. Had Ronnie gone up the stairs to Kale, then there was a likely chance that they could escape from Turner easily.
Stupidity: Mason should have also removed the other gun he had in his office for display, or he could have removed the bullets from the guns. There is no reason he would have to use these guns for his victims, so it makes no sense to leave the other gun in his office or have them loaded with bullets.
Stupidity: If Gabriel and his crew are such incredible hackers, why in the heck would they use a government vehicle that is LoJacked? Even so, wouldn't they be cognizant enough to disable the GPS tracker just in case?