Here is the worddss from B&N’s Unbound: eReading Blog:
More good news on the eBook front: We’ll soon accept Barnes & Noble gift cards as payment in our eBook store.
This change — effective in mid-December — will allow customers to use physical gift cards and online gift certificates to purchase eBooks through our site, through nook, and through other devices using the B&N eReader software.
We’ll have full details (including the specific launch date) in mid-December.