Continuity mistake: When Bumblebee is captured by Sector Seven, the camera goes back to Optimus Prime talking to Mikaela and Sam. If you look at her hair, it is loose and flowing. In the next shots when Sector Seven capture them, Mikaela's hair is tied up at the back, she had no time to tie it up.
Revealing mistake: When Devastator (the tank-bot) is activated and exits its base through a fence, the upper, obviously-rubber, cannon barrels wiggle around. (01:39:15)
Continuity mistake: Mikaela gets a tow truck to move Bumblebee after he lost his legs. At first, the writing on the left door says 'Mike's Towing - 800-555-0199.' When she gets out to hoist Bumblebee up, the writing on the same door has changed to 'Mike's Towing - 800-555-MIKE'.
Continuity mistake: In the beginning of the scene where the Decepticon is on Air force One they show a 747 but when they land and they show the Decepticon sneaking off the plane the Air Force One shown is a KC-135. Although you don't see the whole plane, the engines are that of a KC-135, long and slender versus big and round like a 747. Also, you can see the refueling boom, which a 747 does not have.
Continuity mistake: When we hear Sam's recording on his phone, it sounds nothing like what he actually recorded.
Revealing mistake: When the bus splits after Bonecrusher smashes through it, you can see that it has no seats or passengers. (01:50:35)
Continuity mistake: In the city, after Ironhide flips over the missiles that Devastator shot at him, he can be seen falling very close to the ground, but in the next shot, he is much higher up so that he can then shoot himself back up-right.
Revealing mistake: When Bonecrusher throws the car off the car-carrier, you can see that the underside is just a flat black-painted surface with no gas tank. (01:49:55)
Factual error: In the scene in which the US Army SpecOps survivors of Qatar are being picked up, they were sent a Huey. However, the US Army has replaced the Hueys with the Blackhawk.
Visible crew/equipment: When Sam falls on the sidewalk with the cube and the machines start coming alive during the fight scene in the city, a fast shot shows a cameraman with the camera on the hands on the right side of the screen. (02:02:16)
Continuity mistake: After Megatron says to Optimus: ''Then you will die with them!'', Megatron throws Optimus away, and the latter one heavily damages a car, and two others skid sideways in order to brake in time. Two other cars remain parked. But in the shot where Optimus gets back up and draws his gun, only one car remains. Even if the two cars that stopped just before they hit Optimus drove away, there would still be two parked cars and one heavily damaged one. (02:01:00)
Continuity mistake: When Optimus is holding Sam and Mikaela during Sector Seven's search for them, Mikaela falls, and in the shot facing up Sam hangs onto Optimus with his right hand and grabs her with his left hand. In the next overhead shot Sam now hangs onto Optimus with his left hand and holds Mikaela with his right hand. (01:26:10)
Continuity mistake: When Simmons leads the way into the room with the old Army radio console, he pushes open the massive doors with Keller and the rest behind him (we see the very distinctive wall opposite those doors). When Frenzy pays them a visit at those doors, just as Simmons shouts, "Burn, you little sucker!" in the overhead shot, that side of the doors (in the hallway) is once again visible, only they look completely different now. (01:47:25 - 01:49:15)
Continuity mistake: Just as Mikaela comes to the rescue with the reciprocating saw, when she holds the saw up in front of her face just before she starts to hack away at Frenzy, the saw's blade clamp assembly is about 8-9 inches. After Sam kicks Frenzy, the saw on Mikaela's shoulder has a different configuration with a shorter blade clamp assembly unit. The blade differs as well. (00:54:25)
Continuity mistake: When we hear the Qatar base commander say: "4500X, something's not right," we see the sun has already set (the sky is purple) but when everyone starts to mobilize, the sun is still visible above the horizon.
Continuity mistake: When Bumblebee is caught and then frozen, you can tell that he isn't animated and is rather an enormous prop, because he is a lot cleaner than his animated counter-part.
Continuity mistake: In the scene in the interrogation room with the two programmers there is a big plate of doughnuts which the hacker eats very quickly. But take a look at the plate between shots when he's talking and you'll see that the amount of doughnut left on the plate varies greatly: Sometimes there's one whole doughnut left, other times, in the same conversation, there's only crumbs.
Continuity mistake: When Captain Lennox's wife is watching the broadcast saying that everyone at Qatar was killed, the door is wide open. When she sits down to feed her baby, the door is now closed and the high chair has been moved accordingly.
Continuity mistake: In the scene when Sam is being chased by two dogs and is led into a strange-looking place, when Sam climbs on top of a barrel, notice that the dogs disappear once Bumblebee drives in. Also notice that when Bumblebee drives into that place, he does a 180-degree slide, and in the next shot he's seen circling around Sam. (00:34:10)
Continuity mistake: When the news crew is interviewing Sam's parents during the credits, the way Ron holds Mojo changes. (02:15:10)
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.