Twitter resisted Facebook's overtures, in part because it questioned the valuation attached to Zuckerberg's social-networking site, which was based on the $240 million Microsoft paid for a 1.6 per cent stake in the company last year, when the stock market was riding high and the credit crunch was but a twinkle in Gordon Brown's eye.

But, perhaps more significantly, Twitter's founders also felt they had some unfinished business to attend to with the site; that its full potential as a communication platform – and a money-making enterprise – was yet to be realised.

Twitter has enjoyed an explosive rate of growth in the last year, with the registered number of users now topping six million, a 600 per cent increase in just 12 months.

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