What happens if you give your credit card for the shipping because you think you're getting the free product?
What you really could be doing, if you don't look at the fine print, is agreeing to some type of membership. Or you are agreeing to buy more products in the future.
Many times, this can be legal because it is in the fine print or at the bottom of the website.
Sometimes these offers are using celebrity pictures without permission
If you think this happened to you, you should file a report with the Better Business Bureau or the Federal Trade Commission.