  The puzzling features of recent photoemission data in cuprates have been
object of several analysis in order to identity the nature of the underlying
electron-boson interaction. In this paper we point out that many basilar
assumptions of the conventional analysis as expected to fail in small Fermi
energy systems when, as the cuprates, the Fermi energy $E_{\rm F}$ is
comparable with the boson energy scale. We discuss in details the novel
features appearing in the self-energy of small Fermi energy systems and the
possible implications on the ARPES data in cuprates.
