If you haven't thought out your response, and you hand over the names of co-workers or friends, your actions might backfire, despite your best intentions. I like to know why a headhunter is calling me, where he got my name. A job search is a private matter, particularly if your employer doesn't know you're looking.
Headhunters are reputed for doing things however they want.
You've got to be careful. The sales pitch is what varies. Most headhunters generally start off asking questions about the people they've called. You're one of those folks. If the person is a fast talker in a big hurry with no real interest in you, hang up.