We started out with points at OKW and then because of the booking windows and when we want to visit Vero Beach and Hilton Head - we bought points at those resorts.
All our points (2 contracts) are at the Boardwalk. We have stayed at all the resorts with the exception of BCV (and that will happen soon enough) and love them all. We would not get any value out of owning at different resorts (with the exception of the extended expiration date available at SSR and presumably newer properties). If you book significantly in advance and are insistent about where you want to stay, owning at that resort is certainly of some value....we are just not picky, I guess (although, getting "stuck" at the Boardwalk would NEVER bring a tear to my eye!)
This poll will have huge selection bias as I'm sure DIS members are much more likely to own at multiple resorts than other members. I bet only a very small fraction of all dvcers own more than one. Like 1% would be my guess.