I have a slightly different perspective on fractional ownership because I work in a tourist area with a hurricane season. Fractional ownership is extremely well-regarded by the industry and tourism promoters for a reason that I think demonstrates its fundamental failing as an investment. In my area, the political consensus has grown strongly in favor of promoting fractional ownership to tourists for the simple reason that fractional ownership locks people into returning here, year after year. (And I can hear the time-share promoters already preparing their responses now: "time shares are flexible, you can exchange them for other properties elsewhere, etc. etc..") But the bottom line for the developer is that once the new "owner" has signed on the dotted line, he or she has committed to filling a room or an apartment of the developer's hotel from here to eternity, for an extremely limited upside (if any) and an endless (although admittedly low level) downside (fees, maintenance, etc.). Of course it's a great deal for developers. They tell me it "smooths" out industry downturns (because even if the national economy is horrible, the "use-it-or-lose-it" nature of time shares makes people return whether they want to or not -- or even can afford to or not); it minimizes the impact of hurricanes on tourist revenue (no matter how bad the town looks after a hurricane, people will come back to use their time share time so as not to lose it); and finally, time-shares turn time-share owners into self-interested promoters (or shills) of the areas they've "invested" in (because once you're in, you're in -- so you might as well build up the area.)
For all of these reasons time-share salespeople are paid exceptionally well, short-term rewards to time share "investors" (like a new car on signing, etc..) are exceptionally "generous", and there are so many "free lunches" offered to potential time-share buyers.
As my mother always said, there's no such thing as a free lunch. Getting past the numbers argument for fractional ownership -- which never really works when one factors in the long term -- the very fact that the tourism industry wants to lock you into returning year-after-year to some product the developer controls should itself be the warning sign. Why should you as an "investor" sign up to stay at the same hotel year after year until you're old and gray, when in fact the developer commits to very little? I'd recommend renting every year. You will save money, save hassle, and avoid having to rent in years when you are ill, bored with the place you're considering, or don't want to fly through a hurricane to get there.