Bias towards purchasing tangible vs virtual goods
Grabner-Kräuter et al (2003) suggest that


  Lack of trust is one of the most frequently cited reasons for
  consumers not purchasing from Internet vendors.


References


Grabner-Kräuter, S., &amp; Kaluscha, E. A. (2003). Empirical research in on-line trust: a review and critical assessment. International Journal of Human-Computer Studies, 58(6), 783-812. http://dl.acm.org/citation.cfm?id=941185