According to http://tickets.london2012.custhelp.com/app/answers/detail/a_id/31642…
What can I do with tickets I no longer want?
Updated 09/02/2012 05:31 PM
What can I do with tickets I no longer want?
Our ticketing policy states that tickets are non-transferable. However, providing you as the lead booker are contactable on the day in case of query, a member of your family or a friend may use tickets you can no longer use.
Alternatively, you will have the opportunity to resell your tickets at face value through the official London 2012 ticket resale programme. This is the only authorised way you will be able to submit your tickets for resale.
The first resale opportunity has now closed. There will be a further opportunity to submit you tickets for resale in the Spring.
So you can sell them as long as you’re contactable on the day, or there’ll be another round of selling to come in the spring (isn’t that now?!?)