Most (but certainly not all) payment analysts and insiders consider mobile payments in some form to be a matter of when, not. But even among those who believe mobile payments are a foregone conclusion, the question of when we'll see wide adoption is a matter of contentious debate.

In a post on Into Mobile, Dan Shulman, American Express' group president for enterprise growth provided his rather conservative answer to that question; according to Shulman, we're still four to six years away from wide adoption of the technology.

Shulman's comments came during a dinner in San Francisco with other Amex execs. His assessment of the timeline for mobile payment came as part of a discussion on the company's larger mobile payment goals. According to the article, Shulman sounded bullish on mobile payments in general and American Express' future in digital payments. However, he acknowledged that both consumers and merchants need to update equipment to accommodate technologies like NFC, a process that he said may take five years.

"I’m pleased with our progress but I will not underestimate the amount of work that needs to be done," Shulman said in the post.

American Express has recently been working to shed its image as a conservative, business-oriented payment card. The company launched Serve last year, a mobile-oriented, PayPal-like digital payment platform. It is working with location-based marketing service Foursquare to offer cardholders discounts based on where they're shopping. And it recently launched a program with Twitter offering discounts to Amex cardholders.

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