Keep in mind, study… although it is technically free for the 14 day period (here in the U.S.) as Chris states, to sign up one must still give them a credit card and other information. If you decide to resign within 30 days following the expiration date of the 'free trial' period you may do so, but if you don't then your stuck with the charge for whatever service(s) you signed up for.
I think Ancestry is generally a good site, one has to be cautious when signing on to assure that, if you don't want to continue, that you actually apply for leaving… within the prescribed time period.