Unpaid internships were around years back when I was in college, but it didn't seem like the "employers" viewed the interns in the same way they viewed "real" workers in that they weren't worked into the productivity and income forecast projections the way they are now. They were viewed more as students who were there to watch how things were done (and to do little support tasks that weren't particularly critical to organizational functioning. Interns in those days were helpful to have around, from the employers perspective, but they weren't going to be making money (or, in the case of non-profits, working as a full-fledged, pull-your-weight worker) for the company as interns. I've talked to a few recent-ish college grads who've held down internships while looking for jobs, and that doesn't seem to be the case anymore. They're looked at and factored into company strategy as though they were paid employees, or so it seems to me.