I suppose if it is 'voluntary' and therefore unpaid work, the grad who takes it is still able to claim benefits for not being in paid employment. The $150 is to cover expenses so isn't actual pay if you go by one definition. Seems shakey though.

There are such things as unpaid internships, but they have to be very clear about the role undertaken. It can't just be filing and photocopying, it must involve a large proportion of learning about the company and working environment, like shadowing senior management or something.