"[F]or those in poor health or who fear their underfunded defined benefit plan may default (and don't want to rely on PBGC backing), the new rules have taken a potential buyout offer off the table. And ironically, while the purpose of the new rules was to shore up protections for pensioners, the elimination of yet another means by which plan sponsors can 'de-risk' their pension exposures may only serve to further accelerate the slow-motion demise of the defined benefit plan altogether."