Factual error: The scene where Nightfox steals the Faberge Egg is all wrong. A laser security system must have a photoelectric receptor at the other side to detect if somebody pass between the two devices. As shown in the film, the laser beams points everywhere, so the system can't work and somebody could cross a beam without starting the alarm. Even if it was some weird system based on measuring distance it wouldn't work - if the laser hits the floor at an angle it won't bounce back to the source, it will reflect towards the ceiling.
Factual error: In the movie the poles which houses are built on are situated in the water; one could swim between the poles. That's totally impossible: the poles are drilled in very wet sand (to be compared to a swamp) and you can't reach them from the canals in any way.
Visible crew/equipment: When Ocean tells the Nightfox about the fake Faberge, there's a shot of the Nord Train. When we see the left side of the train, watch its window and you will be able to see a camera and a cameraman reflected.
Deliberate mistake: Laser beams are normally not visible, except for a small dot where they hit a surface. Even if made visible, using smoke or dust or special glasses, they are thin as threads. Obviously something more visual was needed for Toulour's dance act, hence the thick beams of light.
Continuity mistake: Before some of the group is arrested, Brad Pitt is sitting at a restaurant table and 4 cops approach him (2 from the front and 2 from behind). In one shot, the two cops in the front are seen about to sit down, but in the next shot, they are just arriving and aren't even close to the chair. (01:18:50)
Plot hole: How does Agent Lahiri know that you needed to raise the pylons before it was possible to make the cross bow shot the boys needed to unlock the house in Amsterdam? Additionally, those pylons would not be accessible through water as they are planted in mud under the foundation of the building, not water.
Other mistake: When Bruce Willis enters the hotel room in Rome to see Julia, Matt Damon reacts twice with surprise when he turns around and sees Bruce.
Visible crew/equipment: In the scene of Matsui's interrogation, you see Catherine Zeta-Jones leave the "pre-interrogation room", walk behind a glass through a corridor and finally enter the interrogation room; in the last seconds of her walk, you can see the shadow of the moving camera on the two-way mirror.
Continuity mistake: When Tess is told to put a pillow in her dress to make herself look pregnant, they hand her a square pillow. When she takes the pillow out later while a guest of the local jail, the pillow is round.
Suggested correction: The square pillow was in the limo; the circle pillow could easily come from the hotel.
Suggested correction: Talour would need to see the beams in order to get through. I would attest that he let off a low grade smoke canister with a fine mist like a concert hazer to make the beams visible yet not trip a smoke fire detector.