I will be speaking on Tuesday at the ProActum OpenMeetup in Pub Angleterre, Helsinki. (Drinks sponsored by Novell.) The title is "Open Core - What is an open source business model and what isn't? And who cares?".
A bit unusual for this kind of meetup, but I actually summarized my talk into 3 slides, which I will share as printouts with the audience.
I decided to label Open Core as a "Wannabe" business model, meaning that these products want to label themselves as open source while they are not.
The issue of Proprietary SaaS services - such as Canonical's Landscape and Ubuntu One, and Red Hat Network prior to 2008 - hasn't seen as much debate and criticism as the Open Core one, but it seems that if you want to categorize it on a chart like this, there is no such but to label it as a "Wannabe" too. Even if people are not protesting as much against those services, if you really have to form an opinion, there is no way around it, they are certainly not open source.