There’s quite a fight going on in the comments of Elliot Jay Stocks’s A conversation with Erik Spiekermann. If you’re able to wade through the mudslinging you’ll find some good points in there, like this paragraph by Erik himself:
Design is first and foremost an intellectual activity which has nothing to do with what medium you work in. It is about looking at a problem, understanding it, translating it into visuals, actions, and messages. That is solving the problem, whatever medium the solution may end up in.
The worst work is done by designers who have decided on a medium before they even know the problem that has to be solved. Just like a print designer (and I do not make that distinction myself) should not immediately think brochure or poster, an interaction designer should also be able to think about other media besides websites or apps. Otherwise you end up behaving like the infamous hammer: every problem looks like a nail.
This relates to a point I made earlier that we shouldn’t let technology or devices (what Erik calls “the medium”) guide product decisions. The problem and the use cases should guide those decisions.