Risks -
The biggest, but least probable....the member holds the reservation at all times. They can cancel on you the day before you arrive. Its a priivate transaction and Disney will not get in the middle of a dispute.
More probable -
DVC cancellations are far different than CRO - although each member may determine their own cancellation policy, its probably best to think of this as a final transaction. If you need to cancel, don't intend on getting your money back.
Things you should know - DVC books almost completely almost all the time. That means availability can be limited. Home resort owners can book eleven months out, at seven months any DVC owners can book any resort - if there is availability.