It would obviously have to be between to people who trust one another, and this is a game that goes to a higher level of intensity. The info would not have to be TOO personal. Just the threat, within a fantasy scenario, of identity theft, something like that.
Have the 'ler threated to take the credit card and PIN to the nearest ATM and withdraw $200. When the 'lee finally breaks, the 'ler does exactly what he says. Or course, later in the day the 'ler could put back the money, and repay the ATM fee, and take the 'lee out to an awesome dinner. But - as long as there is a mutual trust at this level of play - the 'lee doesn't have to know ALL of the surprising details.
But it should be "real", too, since there is a way out for the 'lee via revealing the personal info. as long as the relationship is healthy.... one of those healthy relationships where people tie each other down and physically abuse each other for fun.... the power ultimately rests in the 'lee for the torment to cease.
But I love that you are mulling this over..!