It is pointed out that some misunderstandigs concerning the theory of electron-positron interaction are an obstacle in a reliable experimental determination of the annihilation characteristics in simple metals. A two step program of reaching progress in this direction is proposed. First a definitive conclusion concerning the applicability of the consequently many-body approach of Arponen and Pajanne in describing positron annihilation in metals. Then a precise determination of the momentum dependence of the enhancement, since the approximate biquadratic formula of Kahana, generally and uncritically used by experimentalists, differs in an essential way from the exact solution of the Kahana equation.