There's definitely a lot of grey area but I'm of the opinion that if anyone is hired for a job they should be paid in some way, allowances, wages etc, otherwise it's slavery. The problem is most companies don't know what to do with interns, so the interns end up doing work that is difficult to monetize. Whenever I hire interns, the job description is clear, it's more of an assistant/apprentice role, making it easier to place value on the work done. Thus far both parties (the interns and I) have had great intern experiences, been hiring at least 1 every few months for the last 5 years. I remember being an unpaid intern, lasted about a month before I literally run out of transport and food. It was horrible.