Right after Facebook began testing a Buy button that enables its users to make purchases straight from their News Feeds, Twitter strikes back with the news that it has acquired CardSpring, a mobile payment start-up whose platform could let developers build credit card-linked offers such as electronic coupons, loyalty cards, and virtual currencies. With this acquisition, Twitter is no doubt betting on its mass platform, with its innate blurb-y style and targeted hashtags, to effectively distribute those integrated offers. In this tight race towards social e-commence dominance, this move might just give Twitter a little edge over Facebook.