Well, I was working on core services, together with fulltime employees (pair programming), after the first two weeks and at the time, they did a lot of pair programming anyway. After two months, I was basically working on my own, but I like to think that I added value much sooner.

Having said that, I don't disagree - it definitely does have a rampup time and I don't disagree with that theres a market and value in unpaid internships, especially short term ones - I'm just saying that I also think theres value for employers and candidates alike in paid internships too.