The more I think about it, the more I think that content is chiefly a legal construct. By this I mean no moral--lots of 'constructed' things exist, or at least survive, thanks to laws--including countries, marriage, etc. Social institutions like these fade into the background as we learn to take them for granted, becoming part of our common sense. There is no point in criticising institutions simply because they are 'constructed' (what isn't?); but when their underpinnings become vulnerable (in this case, the difficulty of copying content) interesting things happen. Again, I claim no originality in this.
The key thing to keep in mind, I think, is that what is important about institutions is the practices that they enable; without these the institutions are meaningless (you could even say that they are the same thing). The practices enabled by content are at least two: it allows content owners to make deals with consumers and with each other; and it allows consumers to play back content they 'own' whenever they want (provided the content and the devices are handy).
Recent technological changes mean that content owners have less control over what consumers can do. But they don't mean that the consumer practices are going away (although they will change). The challenge for content owners is to reinterpret their consumer propositions not in terms of content units but in terms of the consumer practices that they enable. And (see my previous post) I propose that there is still a market for that.