This is a partial answer, but there are a number of academic studies on this topic. The findings of the Berkeley article "Long Tail or Steep Tail?
A Field Investigation into How Online Popularity Information Affects the
Distribution of Customer Choices" (Tucker and Zhang, 2007) suggest that
evidence of a complementary effect, where
the steep tail indicates new interest in the most popular vendors from outside, with
negligible cannibalization of interest for less popular vendors. The ndings suggest
that popularity information can serve as a powerful marketing tool that facilitates
product category growth. They also explain the prevalence of rm practices to highlight
where 'long tail' refers to customers buying low-volume products and 'steep tail' refers to the flocking to popular products.
A couple of key conclusions from that study:
We find strong evidence for a steep tail effect, where customers are more likely to click
on the most popular vendors when the popularity information is publicized and made salient
through ranking the vendors on the page by popularity.
and that there was little negative effects to less popular product sales
If a steep tail effect exists, and if it complements the long tail, websites such
as Google.com and Digg.com can increase overall number of clicks at little cost to the less
A caveat of sorts is stated in the article "On the Depth and Dynamics of Online
Search Behavior" (Johnson et al. 2004) in that their study showed a bit of 'consumer inertia', in that their study
show that the amount of online search is actually quite limited.