"New Facebook Feature Allows User To Cancel Account. ... The company later confirmed that account closures would not stop Facebook from continuing to acquire, permanently store, and sell all information about its current and former users until the day they die." https://www.theonion.com/new-facebook-feature-allows-user-to...
That bug would be a critical failure and be caught, the reverse would be a non-critical bug that the PM decides to to put in the backlog because reasons. If in a year we haven't gotten around the fixing it, then it's time to clean out that backlog!