In a tough and competitive job market like this one, many students are happy just to get their foot in the door at a big company - even if it means working for free and getting by on peanut butter sandwiches and ramen noodles. Although this type of free labor is still relatively common, it poses some legal problems for employers - namely that employing someone at menial work (which many internships entail) without compensation is a violation of federal labor laws.
According to the U.S. Department of Labor, if an intern is to work for free, he or she needs to benefit from the arrangement and not just provide free labor for a company or displace regular paid workers.