A very interesting puzzle about the origin of electron and positron cosmic
rays is deduced from the latests experimental results. We model the propagation
of such cosmic rays in terms of a successfully tested two--zone propagation
model. Several theoretical uncertainties -- like ones related to propagation --
are considered to study different types of electron and positron sources: dark
matter annihilation, secondary production, and supernova remnants.Comment: 3 pages, 1 figure. Proceedings for conference "Topics in
Astroparticle and Underground Physics" (TAUP2009). Rome, July 1-5, 200