Buying a friend a cup of coffee is now as easy as sending a tweet -- and sharing a slate of personal information with Starbucks.

The mega coffee chain rolled out the beta version of its new “tweet-a-coffee” program Monday morning to some fanfare. The conceit is simple: send a message to @tweetacoffee to buy a gift card for a friend. In reality, this is a pretty big deal -- think of the potential if every major company monetized Twitter that way.

@tjortenzi, @caitlindewey just tweeted you a coffee! Redeem it now. https://t.co/sYqqbIkzWS

— Tweetacoffee (@Tweetacoffee) October 28, 2013

@Tweetacoffee works like this: Both senders and recipients must have an account on Twitter, and the sender must have an account on Starbucks.com. After linking the two accounts and entering credit card information through Starbucks, users can tweet a “coffee” -- i.e., a $5 Starbucks gift card -- to friends and strangers of their choice, initially using the program’s Web site and then with tweets sent directly from Twitter. The recipient then gets a message from @tweetacoffee, with a link to an e-card she can redeem by phone or print-out.

(Starbucks)

This all sounds very convenient and fun, of course, until you get into the details of how Starbucks benefits. On the most obvious level, it's leveraging social and mobile media to sell more coffees with less friction -- a move not dissimilar to the way you can donate to charity by text.

But Starbucks is also collecting lots of user information. Notably, both the sender and the recipient of tweeted coffees have to grant Starbucks broad access to their Twitter accounts, including the ability to post tweets. By going to Starbucks.com and creating an account, furthermore, consumers share personal information with the company. Per Starbucks’ privacy policy:

• If you create an account - your username, password, your city of birth, your birthday and mobile phone number.

• If you buy goods at our stores or through our programs or otherwise - what you buy, where you buy, how frequently you buy and rewards you earn.

• If you use our mobile applications to buy goods using a Starbucks Card - information such as your device ID, your location and stores near you and visited by you may be collected.

• If you take a survey or interact with us in various other ways - demographics information and information about subjects that may interest you.

So basically, in the process of tweeting a coffee to a friend, you can potentially tell Starbucks who you are, where you live, who your friends are, what coffee you drink, and which Starbucks locations you visit or don’t.

Starbucks doesn’t sell that information to outside vendors. But it still seems like a grim vision of our big data future ... not to mention a great reason to buy your friends coffee the old-fashioned way.