For the one that I am most familiar with (Goodbarry), traffic to the site is not an indicator of anything. You might as well measure visits to their office.

It irritates me when I see a list of startups with traffic estimates beside them. (A) Traffic doesn't necessarily indicate anything. (B) Traffic isn't a useful comparison unless they are doing the same thing. IE if you are comparing newspapers to newspapers or online Shops to online shops, fine. But this is comparing one company selling enterprise software at 20k per customer (that may never see the site) to one selling books online to another that writes a blog. It's ridiculous.

Exon Mobil gets fewer pageviews then Google.