The card has, not surprisingly, attracted a stellar membership Celebrities such as Nelly, Jay-Z and Paris Hilton have all recently name-checked the card in music and film. Kanye West even included his experiences with the card in a recent song: 'She was like, 'Oh my God, is that a black card?' I turned around and replied 'Why yes, but I prefer the term African American Express'.  Most marketers can only dream of this kind of celebrity endorsement and buzz.

But the Black Amex's ongoing success depends on it maintaining its ultra-exclusive membership and secretive profile. If the card becomes ubiquitous, it risks losing its target market and the partner companies that offer freebies in return for access to the world's elite customers.

 A direct marketing blunder last year saw a top-secret mailing sent to 250,000 regular Amex customers, rather than the 10,000 Black Card holders it was intended for.

It recently featured in the most mass-marketing vehicle of all - a Bond product placement. When Daniel Craig's Bond checks into The Ocean Club in Casino Royale he pays for his room with his Black card. Hence, co-create your brand by collaborating with your consumers.

On the other hand, take the British Airways Black Card for example. BA has three tiers in its frequent-flyer programme: blue, silver and gold. But above gold, and in utmost complete secrecy, there is also a black card, reserved for the 200 customers BA deems to have 'status'. If you are the chief executive of a firm whose employees fly a lot with BA, a key member of parliament or a super-celebrity, the card is yours. Owning the BA black card means you no longer need to worry about customs or seat reservations; you will be whisked straight to First Class. The greatest weakness of the card was that most people did not know it existed. It was purely a card with no pre-seeding, and myth building efforts, and therefore, none of its buzz.