Speaking of which, I've been wondering: what happens if you own DVC and then get banned for life from WDW? Will they buy it back from you? Can they ban you from property that you partially "own"?
I'm not sure what you mean by "ban." I suppose that on one hand you have general trespasses (misdemeanors, finite in duration), and on the other hand you have a private company that could simply decide to deny you admission (indefinitely).
First, having a right to possession and occupancy does not necessarily constitute legal ownership. For example, most people refer to "their house," or "their car," although those items are not "their" property until paid in full. If I am staying at a Disney Resort, and I invite you to "my hotel room," the more accurate description would be "Disney's hotel room." Depending on the nature of the offense, Disney could try to "ban" someone from specific parts of the property (such as the parks), but not "their" specific part of the property and common areas, but this seems rather unlikely given that it's a piecemeal approach to controlling who is - and is not - allowed on property.
I have not read the DVC paperwork, but I am guessing that issues such as this are governed by the contractual documents. And issues not specifically addressed are often reserved for arbitration, etc. A more simple scenario would be a person staying at a Disney hotel and then, for whatever reason, they are trespassed or otherwise "banned" and thus unable to use the remainder of their hotel reservation. Or a ticketholder/passholder with remaining days left on their park admission ticket, etc. Someone's criminal act probably forfeits any monetary value, whereas Disney's "ban" on someone without a stated reason may constitute Disney's breach of the person's contractual license for admission, for which Disney may be liable for a refund. If I purchase a ticket to see the MMC live on tour, and the show is cancelled or the security guard doesn't like my face and refuses me admission, then I get a refund. If, however, I get into a fistfight with someone at the show, and I'm kicked out, I'm not eligible for a refund, even if the show hadn't started yet.
Generally speaking, once a person has a right to possess and occupy a property, then trespass (or a "ban") is not the appropriate remedy to preclude that person's presence on the property. Instead, the property owner must utilize proper eviction procedures before prohibiting the person from accessing "their" property. Under these circumstances, a trespass would be a misuse of criminal procedure, and that behavior (of misusing the law) is greatly disfavored by the courts.
Anyhow, the above is just some general info and not to be construed as legal advice.