What bothers me about this though – and I could be way off base here – is that it doesn’t sound like some of these unpaid internships are purely educational. It sounds like they often do work for the company that the company would otherwise hire a paid worker to do. With a college degree, it’s explicitly a fee-for-service model where you pay X amount for tuition, room, and board and if you pass your classes there’s a degree at the end.
With these unpaid internships, you’re paying for the opportunity to work and presumably learn about the industry, and you’re also effectively donating to the organization the fair market value of whatever work you’re doing. If the purpose was purely educational I wouldn’t see anything sleazy about it, but it sounds like at least some of the time the interns are displacing paid workers.
(I realize that the interns themselves do get a lot of value out of these experiences regardless though.)