Internships and the Law

A couple of weeks ago, a professor kept urging me to go find myself an unpaid internship so that I could get more real-world experience. Despite the fact that my work schedule and my finances allow me to do very few things that include extra work and no pay, I got to thinking about the possibility. Today I was pointed to this article, which talks about the very common, but apparently illegal practice of offering unpaid internships. Who knew?

"In order to qualify as an unpaid internship, the requirement is simple: no
work can be performed that is of any benefit at all to the company. That
is, you can not deliver mail, sort files, file papers, organize a person’s
calendar, conduct market research, write reports, watch television shows and
report on them, read scripts, schedule interviews, or any other job that assists
the employer in any way in running their business."

True, the article is from 2007, but I don't know that much has changed in this regard since then. I also wonder what the rules are regarding "volunteers" - and who decides the differences between the two types of work?