Next to the 1 World Trade Center construction site, the American Express Tower occupies the street that its stables were on in the 19th century, when the company was a freight-forwarding operation.

Today, on the building's posh 50th floor, Chief Marketing Officer John Hayes is describing what sounds more like a tech business than a financial institution.

A 17-year veteran of AmEx and newly appointed board member for Silicon Valley stalwart Yahoo, Mr. Hayes outlines how his company is using Facebook, Foursquare and Twitter. While adland has obsessed over what brands should say on these social-media outlets, Mr. Hayes and his team are testing ways to transact there.

AmEx is touting Sync -- a service that translates social-media activity into savings for cardholders -- in TV commercials featuring comedian Aziz Ansari. The spots highlight the "Link Like Love" feature on Facebook, which offers discounts based on what users of the network like.

The TV blitz followed Sync's high-profile debut at...