Forced opt-in refers to a marketing tactic in which individuals are required to actively choose to receive promotional materials or be added to a mailing list, often without their explicit consent. This can occur through deceptive or coercive methods, such as pre-selecting opt-in boxes or hiding opt-out options, in order to increase the number of subscribers or leads. This practice is often seen as unethical and can lead to unwanted spam or unsolicited communication.