Does any evidence show that Smartphone users have poorer memory?
One relevant study by Sparrow et al. (2011) that came out last year in Science was on the "Google effect": When subjects expected that they'd be able to have later access to information, their memory was poorer for it. We can extrapolate to smartphones -- if individuals know they have information at their fingertips, they don't need to worry so much about retaining that information.


Betsy Sparrow, Jenny Liu, and Daniel M. Wegner (2011) Google Effects on Memory: Cognitive Consequences of Having Information at Our Fingertips Science 1207745 Published online 14 July 2011 [DOI:10.1126/science.1207745] (Free PDF)