That article, and Eric Ries' book, define an MVP as a "
version of a new product which allows a team to collect the maximum amount of validated learning about customers with the least effort." A "version of a new product" doesn't have to be a product.
The classic example of an MVP that Eric Ries uses is the explainer video Drew Houston created for DropBox before building the actual product [1]. The video worked as an MVP by helping Houston test his assumptions, but I don't think you could say the video itself was a "product."
[1] http://techcrunch.com/2011/10/19/dropbox-minimal-viable-prod...