Ten years after it was first proposed, the Adler model of the Staebler‐Wronski effect in hydrogenated amorphous silicon (a‐Si:H) remains plausible and elegant. Adler suggested that during illumination, charged threefold‐coordinated silicon dangling‐bond defects capture photogenerated electrons and holes and reconfigure into metastable neutral dangling bonds. We present recent refinements to this model and review the considerable experimental evidence that a‐Si:H has important metastable charge‐trapping defects. Problems with this and other models of the Staebler‐Wronski effect are discussed.