It started as a simple idea based on the assumption that people don't need vacation lodging except for a week or two a year. Take a house, cabin, condominium, or villa, and divide ownership into 52 weeks (in practice it's usually divided into 51 weeks with one week allowed for maintenance). It allows you to purchase the time spent as vacation lodging, and 1/51 of the ownership of the home. The next logical step in the development of timeshare was to be able to exchange time in these places between people who want to vacation in different areas each...