Revealing mistake: Bond escapes from the buried pipeline when two technicians open a hatch from the outside. One tech unlocks the hatch by rotating a large wheel, which drives the locking mechanism. But when he finally opens the hatch, there's absolutely no mechanism attached. There's just a bare axle that the wheel turns on.
Revealing mistake: When the killer satellite rocket reaches orbit, you can see it 'bouncing' up and down as the pieces separate.
Revealing mistake: When Bond escapes from the research facility, guards give chase on three-wheeled vehicles. One of the guards goes off an embankment and wipes out. He sets the vehicle up and prepares to drive off. Bond is supposed to run up, kick the guard off and take the vehicle. Connery is so slow in this scene that the stuntman has to sit on the vehicle and wait for him to run up for the kick.
Revealing mistake: When Bond is in the trunk of the car, being taken out of the lower level of the Whyte House, a trap door opens out into the desert. The car, however, does not emerge from the door, which is never seen, but appears to be simply driving along a road. The 'door' is apparently a silhouette cutout raised in front of the passing car.
Revealing mistake: When the Hovercraft pulls away, you can see a passenger look out his window and wave directly at the camera. (00:16:00)
Revealing mistake: Many times throughout the car chase in Las Vegas between Bond and the cops, you can see skid marks where they tried earlier stunts with the cars on those points on the road. The most obvious is when Bond pulls away from the Sheriff after he approaches the car.
Revealing mistake: In the final fight scene, Mr. Kid is set on fire by Bond and jumps overboard. What hits the water, though, is a dummy: it floats on the surface right after hitting the water (a human body would sink for a few meters before it comes up again).
Revealing mistake: On the oil rig, when Bond tells Tiffany to "shoot 'em" after she gets the gun, three bad guys run towards her. A helicopter drops a bomb in front of them, taking them out, but watch the guy who is the furthest away. The bomb lands a good 20 feet away from him, far enough away not to do any harm. But he crouches a little and stays up, then he looks at his other two crewman a bit puzzled, and then falls down a bit later as he finally realises what he was supposed to do.
Revealing mistake: During the car chase, Bond weaves through a car park, and a police car can't make the turns, sliding into a wall. The wall's covered in one specific point by what looks like a large pale wooden cover, which the police car just happens to slam into exactly.
Revealing mistake: Blofeld is played by an actor that is not bald (Blofeld was bald in 2 previous episodes). He is also played by Charles Gray, who played the part of one of the good guys in You Only Live Twice. [Not really a mistake, given that Blofeld doesn't have to conform to certain physical characteristics. However, an actor playing a good guy then a bad guy over the space of two films rankles a bit...]
Revealing mistake: When Saxby is shot, he has an instant, pre-dried blood splatter on his shirt.
Revealing mistake: When Bond wakes up after being buried in the tunnel, there's light coming from everywhere and shining on the walls; yet, there's no direct light coming in from anywhere, nor artificial light sources on the walls.
Revealing mistake: The fingerprint in Tiffany's photograph is 100% identical to the sample of Peter Franks in her system. It is impossible for two fingerprints to be exactly identical - in terms of the part of the finger it shows and the amount of paint on the print.
Revealing mistake: Before Bond is stopped by the cops in Las Vegas and when he is gunned and drives away, one can see it's not Sean Connery driving but his stuntman.
Revealing mistake: When the guy in the tub gets covered in mud, his swimming cap to protect his head protrudes around the ears. After Bond sprays him with water, the cap is gone.
Revealing mistake: You can see the flame resistant sleeves on the actor or stuntman playing Mr Kidd, just before Bond sets him on fire.
Revealing mistake: After a policeman touches Mrs. Whistler's corpse's face she winces.
Revealing mistake: When Bond pushes the Blofeld look alike into the mud pit his feet have a natural position, the tip resting on the stretcher. Couple shots later, when his body is submerged and just the feet are visible, they are skewed awkwardly to the side as if the ankles were broken, revealing he's been replaced by a dummy.
Revealing mistake: When the orbiting satellite blows up the missile in North Dakota you can see the scientists nearby move freeze in motion.
Revealing mistake: In the opening scene when Bond pushes Blofield in the mud and we see his legs dissappear, they are obvious dummy legs and the feet have changed position.
Answer: If you mean by hiding - why is he never seen normally - then it's because he is a recluse and doesn't like to be seen in public (like Howard Hughes was). If you mean by hiding - why was he not seen during the movie - then it's because he was being held captive by Blofeld and his minions. Spectre didn't want him out and about ruining their plans.
Zwn Annwn