M. Louisa Locke has a devastating post on how freaking impossible it is to get visibility on Barnes & Noble or Kobo. Anyone running or launching an e-book retail site needs to take that post and have it printed everywhere, including their own skin.
It's been said many times, but the devil is in the details: You can't just compete with Amazon by having a "me-too" site up; if you want your retail site to rack up Amazon-style numbers of indie book sales, you need to compete on author service. No one seems to be doing that.