Regarding the number of members,
DVC used to keep a pretty good count but changed the rules a couple years ago. Under the old system, I believe they used to count member IDs. My wife and I are both listed as owners on our contract, thus we have the same member ID and were originally counted once.
Using this system I recall them being near 90,000 "members" and that was in mid-2005. We have certainly exceeded 100,000 "members" using that logic.
More recently they have started citing a figure over 300,000. At the very least they are now counting all owners listed on contracts. But it may go even further than that. Given that some contracts would have a single owner and many others would have a husband/wife listed, it seems unrealistic for the number of members to grow three-fold simply by counting multiple deeded owners. They may be doing database queries to estimate non-deeded children as well.
However you slice it, DVC hasn't been very forthcoming with figures lately. Up thru '05, they seemed to take a great deal of pride in the growth of membership; the ever-growing figure was quoted often and seemingly with pride. I assume the logic was altered to magically make the program seem much larger. Whatever the case, DVC doesn't say much about it anymore.
As for resale contracts, I don't think there's any way to know that. You can dig into the records of Orange County (and the other two counties where Vero and HHI are located) to see the recorded deeds. But I don't believe there is any way to tell a resale contract from a purchase direct from DVC.
Here's the most recent information I've see on overall sales:
http://www.disboards.com/showthread.php?p=21231201