Andrew Savikas (emphasis original):
This is not just about using free digital content to sell physical goods. It's an acknowledgment that what you're selling as an artist (or an author, or a publisher for that matter) is not content. What you sell is providing something that the customer/reader/fan wants. That may be entertainment, it may be information, it may be a souvenir of an event or of who they were at a particular moment in their life (Kelly describes something similar as his eight "qualities that can't be copied": Immediacy, Personalization, Interpretation, Authenticity, Accessibility, Embodiment, Patronage, and Findability). Note that that list doesn't include "content." The thing that most publishers (and authors) spend most of their time fretting about (making it, selling it, distributing it, "protecting" it) isn't the thing that their customers are actually buying.
Savikas also cites Trent Reznor's comments on "what to do as a new / unknown artist." It's a very inspiring piece of comment.