Nick Carr wasn't happy with Virginia Heffernan's characterization of his view on attention spans. Rob Horning nails the real problem (of semantics) on the head:
[T]he metaphors built into an “attention span” or “paying attention” or the “attention economy” imagine a scarce resource rather than a quality of consciousness, a mindfulness. ... It may be that the notion of an attention economy is a sort of self-fulfilling prophecy, bringing into being the problems it posits through the way it frames experience. It may not be constructive to regard attention as scarce or something that can be wasted and let those conceptions govern our relation to our consciousness.