[Kapow]

Tetris is actually an interesting example:

http://tetris.wikia.com/wiki/Random_Generator

Officially branded Tetris games are required to use a "random bag" algorithm where they generate random permutations of the 7 tetrominos, so that for every 7 pieces (aligned with the bag start) you get each type once. You can only get two in a row if they appear at the end of one bag and the start of the next, and conversely there's a maximum of 12 pieces between duplicates (start of one bag, end of the next). Three in a row will never happen.