When it's easier for me to find a PDF version of your book than it is to find a storefront that sells your book electronically, you have failed to make a sale.
When it's easier for me to find a PDF version of your book than it is to figure out if your book is DRM-encumbered, you have failed to make a sale.
When you have a step-by-step instruction sheet for how to download your eBooks using Adobe Digital Essentials and Dropbox you have not only failed but have exploded in a blaze of "what the fuck were you thinking?"
When legally purchasing and downloading your books is demonstrably worse than finding the PDF online you are not failing to make a sale but your authors should file a class-action lawsuit against you for gross negligence and outright stupidity in your online marketing.
Seriously, if it's not "point, click, download" then you seriously need to rethink your strategy.