Heard about the latest David Bowie CD? No, it's not a remake of The Rise and Fall of Ziggy Stardust and the Spiders from Mars. It's a certificate of deposit with a five-year maturity and an annual percentage yield of 7.25 per cent.

Old rockers never die, it seems: instead, they turn into financial institutions. At least, they do if they are David Bowie who, at the age of 53, has lent his name to an online banking operation called BowieBanc.

In fact, the erstwhile Aladdin Sane is not yet taking deposits. BowieBanc is operated by USABanc-Shares.com, a US online bank, and amounts to little more than an optional extra allowing customers to have the pop star's image on their cheques and credit cards.

Even so, it is an interesting phenomenon. Because Bowie, like some other celebrities, seems to be turning into a one-man brand as he stretches his name across activities unrelated to what business strategists might call his core competencies.

In the days when a brand meant the name of a laundry detergent or something in a can, the idea that people could be brands might have been regarded as absurd.

It seems less so today. Last week, another old rocker, Mick Jagger, registered his name as a trademark for more than 20 products and services, from toiletries to bars. His agent said this was just to prevent other people profiting from the use of his name, but nobody seemed particularly surprised at the idea of Mick Jagger as a brand of deodorant.

For years, sports stars and celebrities have made extra money by endorsing products or licensing the use of their names. Michael Jordan, the basketball star, licences his name to Nike for use on its Air Jordan shoes and clothing, and Elizabeth Taylor's name appears on fragrances made by Unilever's Elizabeth Arden subsidiary.

But some well-known people are going beyond mere licensing deals, using their public reputations and the trust of their admirers as the basis for building their own businesses.

In Britain, the best-known example is Richard Branson, who started in the music and entertainment business but has now stretched into airlines, railways, pensions, vodka, cola, cosmetics and mobile telephones.

His name, and that of his Virgin group of companies, stands for an anti-establishment, "us against them" attitude.

In the US, most people would describe Martha Stewart as simply a writer on ideal homemaking and good etiquette, but she has built a publishing, television and houseware empire based on her image as queen of the domestic arts.

Her company Martha Stewart Living Omnimedia secured a list on the New York Stock Exchange last year.

Other examples include Dr C. Everett Koop, the former US surgeon general, who has become chairman of an online healthcare business called DrKoop.com based on the trust he earned during his career in government service; and Terence Conran, who has built an international chain of restaurants and furniture stores out of his reputation as a connoisseur of good taste in eating and design.

Brian Boylan, London-based chairman of Wolff Olins, the corporate identity consultants, says one reason for the emergence of people as brands is that consumers no longer use brands just to distinguish one product or service from another, but increasingly to make a statement about themselves.

"The brand has a role in addition to helping you choose the product. It has a very important role in defining who you think you are," Mr Boylan says.

"In that context, it may be easier in some areas to identify and associate yourself with a person than with an institution."

John Grace, New York-based executive director of Interbrand, the branding consultancy, puts it another way.

As global competition and the spread of technology make it difficult for companies to offer products or services that are noticeably better than those of their rivals, he says, personality has become a more important point of differentiation.

"Brands have two components. There is a functional aspect - what they are, how they operate - and there is an emotional component," Mr Grace says.

"On the functional level, every brand is at parity. Invariably, at any point in time, there is someone else offering exactly the same functional benefits.

So the only thing brands can do to differentiate themselves is to understand the emotional connections that people have to them, and David Bowie is an emotional connection for his limited target audience.

Even so, is Bowie as banker a stretch too far? It seems a long way from his anti-establishment origins as the glittering space alien Ziggy Stardust, who found fame in the 1970s by declaring himself bisexual, making forays into transvestism and inflicting the name Zowie on his new-born son.

Yet there is another side to Bowie. Two years ago, he pioneered a new form of financing by selling $55 million (€54 million) worth of bonds securitised against future earnings from his back catalogue - a move that prompted a slew of other musicians and songwriters to follow his example.

He has also become an Internet entrepreneur, launching BowieNet as the world's first artist-created Internet service provider and becoming a partner in UltraStar, a company that sets up websites to serve fans of other celebrities.

Bill Zysblat, Bowie's business manager, sees no conflict between BowieBanc and the pop star's former image.

"What he is doing is taking his fan base, which 20 years ago had an affinity for wearing a T-shirt of his, and maybe 10 years ago graduated to wearing a golf shirt of his, and in the last three or four years has developed to being part of his online service, and trying to create that same affinity with what he is doing with online banking," he says.

Mr Zysblat points out that Bowie showed his business acumen at an early stage of his career by retaining the rights to his original recordings, known as the master tapes, instead of ceding them to his record company, as most other artists did.

This allowed him to securitise most of the income generated by his back catalogue, instead of just the portion represented by royalties.

"From the earliest days of David's career, regardless of how avant garde he may have appeared to the public, it was never really an anti-establishment message," Mr Zysblat says.

"Maybe we felt it was anti-establishment because our parents didn't like the fact that he was wearing a dress. But quite frankly, if you look at his savvy, going back to his very first signing with RCA where he retained ownership of his masters, the business side of his mind was always working."