Betting on a line with a negative expected value (EV) can be appropriate in certain circumstances, notably when the potential payout aligns with a specific strategic objective or when the bet is part of a larger portfolio that may yield positive returns overall. For instance, if you have strong confidence in a specific outcome based on unique insights or data not reflected in the line, placing the bet may still be worthwhile despite the negative EV. Additionally, such bets can be part of a broader strategy to gain experience or exposure to a particular market.