Insurance (in blackjack): A side bet offered by casinos in blackjack that allows a player to bet up to half of the amount of his bet that the dealer has a natural when the dealer's upcard is an ace. It pays 2:1. -- BJ21.com Glossary of Terms
Basic strategy says never take insurance. Even if you have a natural, you are better off not insuring it. (A basic-strategy player is) better off winning 3:2 most of the time than winning even money for sure …
As soon as you see the dealer’s ace, (a card counter should) begin considering whether to buy insurance. If the Hi-Lo true count is greater than or equal to +3, make the bet. -- Professional Blackjack by Stanford Wong
Question: Is it wise to offer to buy other players' insurance if they let you?
Eight-deck shoe and the Hi-Lo true count was +7. I had my max bet of $300 out and another player -- a high-rolling ploppy -- was betting two purple chips each on two spots. The dealer showed an Ace and only I insured. Dealer turned a blackjack. Later it occurred to me I could have, if it’s allowed, made up to $1000 in side bets on the insurance (I could also have insured for less) on the high-roller's hand. In fact, why not total all the players' bets and insure for half that amount against a blackjack? This seems like a high EV play. Other than getting the pit’s attention, what are the drawbacks?
LV Bear: I’ve made this play a couple of times and would like to do it routinely, but long ago made a decision not to.
You're right, it brings tremendous pit attention, which despite the high EV, makes it unwise. Since you obviously will make this play only when correct to do so, even the dumbest/laziest pit employee will figure it (and you) out in little time. It’s maybe okay no more than once per session when others have a lot of money out there and you're about to leave anyway.
Other problems include comments and questions from the other players, which are harder to ignore once you have, in effect, bet on their hands, at least the way they will see it. Worse, you could have a player try to take your winnings, either through ignorance (thinking you were trying to "help" him save his money, perhaps just because you're a nice person), or outright greed or theft. This will place you, the dealer, and the pit in an awkward position.
Though this seems like a great play at the correct times, I think the potential for problems far outweighs the EV. If you know and trust the other player, it may not be bad. But in such a case, the other player is likely to simply take their own insurance every time you do, since they either know or suspect that you know something they don't know (the count).
Originally published on bj21.com Green Chip, edited for this format.