Over the years I have ejected at least 20 people from poker tournaments I was running for taking chips. During one of the Queens Poker Classic's in the early 1990's, we had to call LV Metro on a player that would not give them back. When he saw Metro walk in, he decided to give up the chips. He was barred from playing in another tourney at the FQ's.

I have had other players come to me and tell me he saw so & so pocket chips. Remember there are always 9 other sets of eyes on you at a poker table. Thats better than the cameras.
Players are very leery of people taking chips off the tables. It is cheating to them.

Everytime there is a colorup, the tourny people knows if chips are missing.
Some BIG names in poker have been caught and barred. One incident at the Orleans got a big name player barred from NV tournaments.