I don't know" means "NO!" "I don't know" means "I'm too cowardly to tell you the truth because I can't deal with confrontation." "I don't know" means please do the dirty work for me because I don't want to hurt your feelings even more then I already have.
Greg Behrendt, Amiira Ruotola-Behrendt (2005). “It's Called a Breakup Because It's Broken: The Smart Girl's Break-Up Buddy”, p.38, Harmony
