Unpaid internships can either be great or the worst thing ever. You can learn your craft with "true" professionals or be chased away from dreams as fast you walking the door.
Radio interns can sometimes be abused via stunts or doing bitch work that no one else wants to do (filing paperwork sucks). An old joke is that you never learn their names because of the turn around on getting new ones.
The Dalkey Archive Press in the UK posted an internship opening back on December 11th and some are calling it "the worst job advertisement ever."