OK so let's say I buy at BWV, what happens when I want to stay at AKL. Do I keep on buying at all the DVC's. I'm sure all you BWV owners have stayed somewhere else.
No, not really. But, it's hard to know when you do/don't need to own at a particular resort until you've spent quite a lot of time learning the system.
For example, some room types are hard to get almost year round, notably AKV Value and Concierge (all sizes), BLT Standard (all sizes), and the Grand Villas at OKW-HH or BWV. BWV Standard/Boardwalk View units in any size are also tricky. They aren't necessarily gone before 7 months year-round, but there will be many times when they are not available.
There are also times of year that are hard just about everywhere, because they are super popular. The first full week or two of December and New Years Eve are both in this category. Marathon Weekend can be tricky as well. For these periods, you want to make a reservation at your home resort at 11 months; switching is a bonus.
Then there are specific times of year at specific resorts that are hard. BWV and BCV during Food & Wine. VWL during the period between Thanksgiving and New Years (it's considered by many to be "the Christmas resort.")
There are probably other times at other resorts that I am not thinking of, but you get the idea. These "hard to get" reservations aren't impossible, of course, but you have to be flexible about dates, unit sizes, and more than a little bit lucky. You can't count on getting them, for sure.
Finally, things can and do change. For example, the Treehouses used to be hard to get year-round. But, as DVC has declared more inventory and rebalanced SSR's chart to raise THV point requirements, they've gotten easier.
The "buy where you want to stay" advice is really most appropriate if, like a few prior posters, you have one specific vacation at one specific resort that you want to take most years. If you really want to stay in the Epcot area for Food & Wine, and do that regularly, you probably need to own at BCV or BWV. If you want access to the AKV concierge floor most stays, you
must own at AKV---and that one is hard even at 11 months.
Conversely, if you don't need to be at any one *particular* resort on a regular basis, I think the better advice is: "Don't buy where you would not be happy to stay." That way, if you are coming during one of those hard-across-the-board periods, you'll be satisfied with your home resort. You can still explore other places when they are available, and have a good chance at sampling all the resorts over time if you are flexible about when you do it. But, any non-home resort stay is one of those "Let's see if that works out" situations, not a "We are definitely going to stay there" deal. So, if you are "stuck" with your home resort, you want to be happy with it.