Starbucks 'Tweet a Coffee' programme has generated an estimated $180,000 in 6 weeks

"A Starbucks program that lets consumers buy coffee for friends on Twitter, has prompted about $180,000 in purchases to date since it launched in late October, according to a researcher.
Research firm Keyhole tracked all the instances in which someone used "@tweetacoffee" in conjunction with a friend's Twitter handle and found that more than 27,000 fans used the program. Some 34% of users bought multiple gift cards and 32% of the purchases occurred on the first day.
Launched on Oct. 28, Tweet-a-Coffee let you give a $5 gift card to a friend by putting both "@tweetacoffee" and the friend's handle in a tweet. To do so, users had to link their Starbucks account to Twitter and their credit card to the account. Saif Ajani, co-founder of Keyhole, says $180,000 is a respectable return on investment since the program probably required a low investment. (Starbucks reps could not be reached for comment on his report.)
Ajani says the real coup for Starbucks is that it now has linked 54,000 users 'Twitter IDs to their mobile phones and customer IDs. "Here's proof that direct-response [marketing] works on Twitter," he says. Even better, Starbucks will now be able to access the Klout scores of those customers and see what topics interest them."

Source:  Mashable, 5th December 2013