Here are the terms from their site, which you can see here.
*Excludes Starbucks VIA® Ready Brew 3-pack and Starbucks® K-Cup® portion packs
Offer valid on:
10, 11, 12 and 20 oz ground or whole bean Starbucks® coffee
6, 7, or 8 ct Starbucks VIA® Ready Brew
Or a combination of three (3) qualifying products
Purchases must be made by 12/31/2011 in one transaction.
Your cash register receipt must be dated between 11/1/2011 and 12/31/11 and submitted by 1/31/2012.
Offer not valid in Starbucks stores.
You'll need to go here to get the form.
(Thanks, Deal Seeking Mom!)