Karnitz v. Wells Fargo Bank, N.A., 572 F.3d 572 (8th Cir. 2009)

(reversal of district court judgment concluding that mortgage was invalid under Minnesota law because both spouses did not sign it; plaintiffs estopped from claiming invalidity of mortgage because nonsigning spouse knew of and intended to mortgage the homestead, retained the benefits of the mortgage and defendant changed position based on assumed validity of mortgage; dissent pointed out that defendant never detrimentally relied on the non-signing spouse's language or conduct in making loan - nothing the plaintiff's did or said caused defendant to lend funds or forego obtaining non-signing spouse's signature on necessary documents).