Originally Posted by WVHillbilly
Movement does NOT occur based on stack sizes. It's only done to keep the tables as balanced as possible. So if 12 people remain in a tourney there won't be a table of 5 and a table of 7, rather 2 tables of 6.
I don't know how they do it online, it's supposed to be random. I can tell you how it usually works live though:
In a casino tournament, the dealer will usually have a card / marker for every seat at their table. If a player on their table gets knocked out, the dealer gives the corresponding seat card to the floor manager. This way, they keep track of where the empty seats in the room are.
When the number of empty seats available becomes equal to a full table's worth of players (so, ten empty seats spread around the room if the tables are playing ten handed), the floor manager will go to the next table on their break-down list, place all the seat cards face down on the table, and the players will pick one of the cards.
That card will tell them where their new seat is - since the players pick their own
cards and they can't see where the new seat is going to be, it ensures it's random. Stack size is certainly not taken into account.