In addition to charging a fee for checking baggage, Spirit Airlines will soon charge fees for use of the overhead bin. http://www.msnbc.msn.com/id/36193399/ns/travel-news/
In order to pay nothing beyond the actual fare and taxes, in addition to not bringing any large suitcases which must be checked, your carryon luggage has to fit in the seat in front of you.
Has anyone ever traveled like this for something beyond an overnight trip?