From Wikipedia:
Perhaps the most famous example of the gambler's fallacy occurred in a game of roulette at the Monte Carlo Casino on August 18, 1913, when the ball fell in black 26 times in a row. This was an extremely uncommon occurrence: the probability of a sequence of either red or black occurring 26 times in a row is (18/37) to the power (26-1) or around 1 in 66.6 million, assuming the mechanism is unbiased. Gamblers lost millions of francs betting against black, reasoning incorrectly that the streak was causing an imbalance in the randomness of the wheel, and that it had to be followed by a long streak of red.[1]
and from the Caesar's Entertainment site:
Think your number or color has to hit soon? The longest recorded streak of one color in roulette in American casino history happened in 1943 when the color red won 32 consecutive times. In a row. The people convinced black had to hit next were absolutely right. Eventually.
That chance is one on two billion, more or less. But how many times has a roulette ball been launched somewhere?