Massively against them if they aren't paid like any normal job. If the intern is doing actual productive work(and let's not kid ourselves - they are most of the time), then they should be paid like any other employee.

The only exception I can see is companies that have training programmes with vocational schools, where you go and work somewhere for say 2 years training to be a carpenter or a plumber or electrician or whatever - then it's no different than being at school and learning. But I'd wager than 99% of internships are not like that, they are just a very cheap way to get unpaid(or poorly paid) labour under the pretense of "giving young people work experience". It's nonsense.