Wait, I missed International Friendship Day? I guess if I had any friends, I would've known. In most countries it's the first Sunday in August. It's July 20 in Argentina (where it's known simply as Día del Amigo), and this year it inspired a novel campaign from women's fashion retailer Todomoda, ad agency +Castro and advertising students at Escuela Superior de Creativos Publicitarios—allowing friends to literally share tweets. An app allowed one friend to start a 140-character tweet and a second friend to finish it—it then appeared in both feeds. There were also games testing friends' knowledge of each other, with Todomoda discounts as prizes. Per +Castro, the campaign was seen by almost 600,000 Twitter users in two weeks, and 4,000 girls and young women took part. That's impressive, though the whole concept—detailed in the happy-happy shop-shop case study below—makes me wonder if "friendship," by and large, has degenerated to the point where it's nothing more than a promotional peg. Help me find the best deals on the coolest stuff … and let's share a tweet, connect on Facebook and split an order of branded nachos at the mall while we max out our credit cards. In today's world, that's what friends are for.