Forced repurchase of mortgage securities and mortgage loans is not just a theoretical litigation risk. I quote: "In the event of a breach of the representations and warranties, the Company may be required to either repurchase the mortgage loans (generally at unpaid principal balance plus accrued interest) with the identified defects or indemnify (“make-whole”) the investor or insurer." The quotation cited above does not come from the talking points of a securities class action plaintiff's attorney: It comes from Citi's 2009 10K.