In my mind, there are two distinct arguments: that copyright is about the moral rights of the owner, and that copyright is economically useful. The moral argument has nothing to do with payment as such; it is all about control.

Agreed, technology has some interesting effects of the notion of ownership: consider sampling and wikipedia to name but two. It affects the economic argument much more than the moral one; technology doesn't so much invalidate the concept of ownership as make certain modes of ownership uninteresting.

edit: spelling