I agree, I would not do business with someone that called me out of the blue. There are a lot of scams out there, especially with the current economy.
The DVC Deeds are public record, so they likely use those to contact members. Even though there are usually no address or phone numbers on the deeds, there may be enough information with just name & state (the notary part often says what type of document was presented for ID, like a Texas Driver's License.) With a computer, it is pretty easy to find people by name and state, unless they have a really common name.