I actually don’t agree with unpaid internships either. If you want someone working for you, you should pay them for their time. Even if its minimum wage.
My first job was at age 13...I swept the floors and shined shoes at a barber shop in my small home town. My shoe shine kit cost $5, and the owner loaned me the money (and deducted 50 cents a week from my pay of $1 a day (from him) plus shoe shine tips till I repaid his loan). I have worked every day since then...I am now 52. Don’t tell me that there are jobs Americans won’t do!!!
I've worked with interns before in a professional (supply chain management) setting. No slam on the interns, because all those whom I've worked with have been nice kids. But the fact of the matter is that for every hour of real work you get out of them doing mundane stuff like entering data and checking spreadsheets, you will spend at least an hour showing them how to do some of the other things (generally more glamorous and complicated jobs) which also have to be done.
Generally, your added workload is at least as much as the workload relief which the intern provides.
So he or she is getting a cheap education at your expense. Most of the companies where I've worked with interns do not add them because they need help with the workload, they add them as sort of a civic responsibility to educate the upcoming generation in the realities of the workplace and, on occasion, get a good look at potential recruits.
In these happy occasions, it is sort of like renting the model car which you are considering buying. In this day and age, when most business don't even want to take a chance on new college recruits, it can be a win-win for both parties.