1. Care about tweeting about their company.
2. Talk like that.
However, I think this could be real if:
1. Amazon has some incentive program that basically allows workers to take on a "marketing assignment" for some sort of bonus. If so, how is this different than contriving good reviews about your restaurant on Yelp?
2. Amazon has developed or is paying for third party software that lets their PR people quickly manage and create activity on multiple Twitter accounts from a central interface.