NEW YORK (TheStreet) - In case you've been losing sleep over when, if ever, you'll be able to buy stuff on Twitter by using your American Express, card - you can stop fretting right now. American Express has announced what it's calling "a new social commerce experience that turns Twitter #hashtags into purchases in a unique and seamless way." The actual process sounds somewhat convoluted. Amex explains it this way: ... Click to view a price quote on AXP. Click to research the Financial Services industry.