Abstract: A ticketing system allows a group of people to purchase individual tickets for an event and sit together even though the tickets are purchased separately. The ticketing system is able to encumber a block of seats and provide a block identifier that allows subsequent purchasers to purchase seats within the block of seats if they provide the block identifier. The block of seats is encumbered for an encumbrance duration, which may be established, or updated, based upon the popularity, or changing popularity, of the event.