Are buyers of mortgage-backed securities getting paid properly for the repayment risk they are assuming in a market awash with adjustable-rate “affordability” products? Researchers at Bear Stearns don’t think so. In fact, in an update published this month, Bear analysts Dale Westhoff, V.S. Srinivasan and Steven Bergantio, suggest that investors may be relying on false assumptions about the interest rate sensitivity of borrowers. “Clearly, there is a disconnect today between market opinion and model…