Blackjack might be the only place where insurance is a bad idea. Insurance costs half the original bet and pays 2:1 when the dealer has a natural blackjack. While the odds for dealer blackjack vary slightly depending on the number of decks in the shoe, the dealer is likely to have blackjack less than one-third of the time. A player might win a bet every once in a while but such wagers lose a lot of money in the long run.