American Express (News - Alert) has teamed up with a group of retailers to offer discounts to customers who sync their AmEx cards with their Twitter (News - Alert) accounts.

Customers simply sign in to AmEx through Twitter, sync their card, and then tweet specified hashtags to a group of merchants. By tweeting, customers will then unlock a variety of special promotions and discounts. For instance, a customer who tweets #AmExWholeFoods after syncing their credit card will receive $20 off their next purchase of $75 or more from Whole Foods.

“I really believe that this is turning tweets into transactions,” American Express executive Elizabeth Rutledge told CNN Money. “We [also] have the ability to give back these great analytics to merchants.” Partners for American Express tweeting promotions include Zappos, H&M, Whole Foods, Best Buy (News - Alert), McDonalds, Seamless, FedEx and several others.

American Express has also had luck with Twitter in the past, teaming up with Foursquare (News - Alert) to offer discounts to local merchants at conferences and other events. However, sometimes Twitter promotions backfire. McDonald’s, for instance, tried promotional hashtags like #MeettheFarmers to promote the company’s guarantee of fresh produce and to focus on wholesome stories about farmers. However, the promotional campaign backfired when customers hijacked the hashtag and started posting McDonald’s horror stories.

McDonald's social media director Rick Wion told reporters that it only took an hour for the company to see that the hashtags weren’t working. “It was negative enough that we set about a change of course.” McDonald’s pulled most of the hashtags from the campaign, leaving only #MeettheFarmers, which didn’t produce significant backlash.

Newspapers are also significant tweeters, with The Washington Post leading at approximately 664 tweets per week. Most reporters use tweets to disseminate their own material or to add additional content. In addition, some news outlets like Fox News solicit information directly from Twitter followers in order to better engage their audience.

“We need to be where our customers are,” Rutledge concluded. “They're on these platforms using them every day.” By offering lucrative discounts and promotions, American Express is making it worth their while.