Audio problem: When Lennox is speaking to his wife via the PC, when we hear him say, "Oh my goodness, look at her. She's getting so big," there is no mouth movement whatsoever. (00:05:05)
Visible crew/equipment: When the base in Qatar is attacked, in one shot two crew members, one with a camera, can be seen towards the left side of the screen. (00:06:55)
Revealing mistake: When Blackout is destroying the base in Qatar, a few Humvees get flipped over, and none of them have engines in them. (00:07:00)
Continuity mistake: In the opening attack scene on Soccent AFB, Colonel Sharp pulls an axe off the wall to literally cut the server hard lines. This axe was not on the wall in the earlier dialogue between Colonel Sharp and the one who was telling him about the unidentified aircraft. (00:07:40)
Continuity mistake: In class for his genealogy report, when Sam begins to dump his great-great-grandfather's belongings onto the desk, while the backpack is upside-down it turns around from front to back, between the wideshot and next close-up. (00:08:55)
Continuity mistake: During Sam's family genealogy report, when he holds up Captain Witwicky's glasses to show the class, there are cracks in certain areas of both lenses. Those cracks actually change position and characteristics when we see the glasses elsewhere in the film, such as on eBay and when Prime explains their importance to Sam and Mikaela when they first meet. (00:10:15 - 00:17:40)
Continuity mistake: After class when Sam rushes to his father, who is waiting in his car, and tells him that he got an A-, the license plate is affixed to the front bumper. At the start of the next shot, the front license plate is gone, but it then reappears when they arrive at Bobby B's. (00:11:35)
Visible crew/equipment: When Sam rushes to his waiting father after class and tells him about the A- they drive off. In the next close-up shot the filming vehicle, with its top mounted crane and camera at its front end, are reflected on the car's surface as they drive past, before pulling into the Porsche lot. As this shot continues, when they drive onto the Porsche lot, the filming vehicle directly behind them (note its headlights), is reflected on the large windows in front of them and when Sam is told he isn't really getting a Porsche the filming vehicle, which is now beside them, is reflected on the window to their left. (00:11:45)
Continuity mistake: When Ron and Sam, followed by Bumblebee, make the U-turn in front of Bobby B's and then park, the spinning 'Bobby B. sez...let's talk deals' sign is to the left of the three vintage gas pumps, near the clown. When Bobby B. puts his arm around Sam's shoulder and says, "Sam, your first enchilada of freedom..." the spinning sign is now on the other side of the pumps, where there wasn't a spinning sign previously. (00:12:10 - 00:13:15)
Continuity mistake: When Bobby B. walks with Ron and Sam to the main used lot, where Bumblebee and the VW Beetle are located, most of the cars opposite Bumblebee and to its side actually change make, color, etc., from the time Ron makes the U-turn, to when all the windows shatter and shots between. Examples are: there is a camper parked in the fifth space which changes to a car; the yellow hatchback behind Sam when he opens the car door changes to a light blue car; and the two blue cars (one with a spoiler) parked beside Jaime, the ostrich, which change to a dark car and yellow hatchback. (00:12:10 - 00:15:10)
Continuity mistake: When Ron and Sam park in front of Bobby B's, there are three cars parked in front of the three pumps - a white vinyl top, a wagon, and a red car. When Sam says, "You said half a car, not half a piece of crap, Dad," the red car has been replaced with an old blue Plymouth, specifically for the "50-year-old virgin" joke, because the red car is back in following shots. (00:12:20)
Continuity mistake: When Sam is looking at Bumblebee at the car lot, he wipes some of the grease off of the Autobot insignia. When Bumblebee blows out all the windows, all the grease is gone. (00:13:55 - 00:14:50)
Continuity mistake: At Bobbie B's, when Sam first opens Bumblebee's driver-side door, the gas pump's white steel guardrail is directly behind him, aligned with the driver's seat, but when all the windows shatter, Bumblebee's front fender is aligned with the guardrail, though Bumblebee has not moved. Same goes for the VW Beetle beside the Autobot. (00:14:00 - 00:15:10)
Other mistake: When checking the eBay auction for his ancestor's glasses, the seller name is listed as 'Ron Witwicky'. eBay would list Sam's user name - 'ladiesman217' - as the seller, not a full name that isn't even his. It is clearly established throughout the film as the glasses are being sold through Sam's own account. (00:17:40)
Visible crew/equipment: When Sam and his friend head for the party at the lake, as they drive by the lake and the camera cranes up to show the lake, you can blatantly see the shadow of the camera on the crane moving up. (00:20:05)
Visible crew/equipment: When Sam is talking to Mikaela's boyfriend, you can see the camera and crew reflected in the Hummers mirrors. (00:20:20)
Continuity mistake: At the park, when Sam decides to drive Mikaela home, Miles is in the car with his right arm (viewer's left) up behind his head, but in his close-ups his arm is down. (00:22:30)
Revealing mistake: When Mikaela and Sam are in his car when he gives her a ride from the lake, both windows are open but her hair doesn't blow around at all - like it would if they were really open. (00:23:00)
Continuity mistake: When Bumblebee "breaks down" on the side of the road, a book appears in Sam's hand that wasn't there before. (00:24:10)
Other mistake: When Sam and Mikaela are parked at the top of a cliff after "breaking down", Mikaela lifts the Bonnet of Bumblebee to check the engine. Mikaela, who's the car expert, states the motor has a carburetor, but the manifold on the engine was one for an individual throttle body fuel injection system. (00:24:50)
Chosen answer: There is no reason to think they can't. They simply choose not to. They may feel it's too deceitful.
Actually in this movie (when joining up with bumblebee and the others after they pick up the All Spark) and Revenge of the Fallen, Ironhide uses holographic humans in his cargo bed. Also, Arcee and the twins use holographic drivers at the beginning scene in Revenge of the Fallen.