In a year that has shaken faith in the business model of financial conglomerates such as Citigroup, Kenneth Chenault, chief executive of American Express, could be forgiven for feeling a little vindicated, writes Matthew Garrahan.

The credit card company used to look a lot more like Citigroup than it does today. In the 1980s it was a financial supermarket, owning Lehman Brothers as well as retail brokerage and asset management divisions.