Reply to any Tweet that contains an Amazon product link with hashtag #AmazonCart and it'll be waiting for you when you return to the site. For the feature to work, a customer must link his or her Twitter and Amazon accounts together.
Not only could this be killer for authors promoting their titles and affiliate marketers, but this approach could work with brands that regularly post product photos and Vine / Instagram videos.
While it reduces friction, the experience is not completely seamless - you still have to remember to visit that cart. The next step would be to trigger mobile or email notifications from idle carts referred from hashtag-commerce. If that book has been sitting in the cart for 24 hours, for example, a trigger -- even a Twitter direct-message -- would be useful.
Will this be a customer hit? Social has yet to prove itself as a shopping medium (remember F-commerce?), but this approach is a step in the right direction in measuring intent to buy through social channels, not just "awareness" and click activity.
An interesting observation mentioned in Adweek -- there's nothing stopping other brands from hash-jacking #AmazonCart buying promoted post placement to appear in feeds. But it's unlikely to rock the boat. "Amazon isn't afraid of competition," commented Lee Maicon, svp of strategy at digital agency 360i. "They relish it."