The amount of dead money in a pot affects the Pot odds of plays or rules of thumb that are based on the number of players. For example, a common rule of thumb used by many Omaha players is that one should raise with a Nut low hand on the last round only if there are four players in the pot, and just call if there are only three. But if there is considerable dead money in the pot, this changes the odds to favor raising even with only three players.
The term "dead money" is also used in a derogatory sense to refer to money put in the pot by players who are still legally eligible to win it, but who are unlikely to because they are unskilled. Can also be applied to the player himself: Let's invite John every week; he's dead money. The term "dead money" also applies in tournaments, when a player enters who has no chance of winning. For example, in the World Series of Poker, many players win their entry in a satellite tournament against good opponents, but have no chance against the top pros they will meet in the main event.