Facebook does not notify users that a simple action such as liking a page would be translated into an endorsement. A cyber citizen would be embarrassed if the liked product was of a personal nature, like a sex toy.
A recent court case won by privacy advocates on behalf of an estimated 100 million Facebook users whose profiles were used in sponsored stories has ordered Facebook to pay 20 million dollars in compensation which amounts to 10-15 dollars per litigant. In previous court cases of this nature most of the money went to charities due to the challenges involved in distributing small amounts to a large number of people.
Facebook will still be able to use your endorsement in sponsored stories subject to Facebook notifying you as we'll as introducing privacy protections which allow users to specify actions that they would not like to be used as endorsements in sponsored stories.
Cyber citizens should be ready to modify their privacy settings and above all should consider the implications of being an unintentional endorser before they like a post or page.