eBay, the online auction site, has bought Skype, the privately-owned internet telephony company, in a deal which could be worth $4.1 billion (£2.2bn) in cash and shares, including a bonus of up to $1.5billion based on performance.

The deal will make multi-millionaires of Skype's founders, Niklas Zennstrom and Janus Friis. The pair developed the software that powers Skype, which allows users to make free telephone calls over the web, two years ago. It has since been downloaded 163 million times.

The move represents something of a gamble for eBay, however.

Skype does not charge users for downloading its software and generates revenues from other services. Last year, Skype generated revenues of $7 million (£3.8m). This year it expects to earn around $60 million, and $200 million in 2006. But the eBay deal comes at a time when the internet telecoms market is becoming increasingly crowded.

Google last month launched Google Talk, its own free voice messaging service, while Microsoft bought Teleo, a net telephony specialist, for an undisclosed amount. Vonage and Yahoo also offer internet voice services.

"All of these companies are coming from slightly different directions and could all play a part in the future of telecoms," said John Delaney, a principle analyst at Ovum, the telecoms and technology consultants.

"Companies such as Google and Microsoft don’t pose an immediate threat to incumbent players such as BT, but they do have powerful brands and could encroach on BT’s turf in years to come."

eBay said today that the deal would strengthen its global marketplace and payments platform, PayPal, "while opening several new lines of business and creating significant new monetisation opportunities for the company".

Meg Whitman, the chief executive of eBay, said it plans to use Skype to launch a "pay-per-call lead generation" service, where companies pay eBay for calls from potential customers generated through the eBay website.

Ms Whitman added that the integration of a voice-calls service into the eBay auction site could also increase its popularity in developing markets such as China and India, where eBay says its users are more used to haggling, more conscious of cost and less trustful of e-commerce sites.

Ms Whitman said: "communications is at the heart of e-commerce and community. By combining the two leading e-commerce franchises, eBay and PayPal, with the leader in internet voice communications, we will create an extraordinarily powerful environment for business on the net."

Skype's free software allows users to talk, free of charge, via their computers' broadband internet connections. The company generates income from subscribers who pay to be able to use Skype to call non-members on traditional telephone landlines. It also charges for services such as voicemail.

Skype claims 54 million registered users worldwide, though only 2 million of them pay fees. Last week Skype told Times Online that it was committed to its business model, pointing out that it had grown faster than other internet giants such as Yahoo. The company claims it is adding some 150,000 users a day and that it is "the fastest growing internet company ever."

The eBay deal marks the final stage in a process through which Skype has sought to resolve its future. Earlier this year it hired Morgan Stanley, the American investment bank, to advise on "strategic options". These included a sale or a potential flotation on an international stock market.

Skype was believed to have held talks with several potential suitors, including News Corp, the parent company of Times Online.

Skype is backed by several American venture capitalists, including Bessemer Venture Partners, Draper Fisher Jurvetson, Index Ventures and Mangrove Capital Partners.

Observers have suggested that eBay's online auction model, after rapid growth, is approaching maturity and that the company is searching for ways of diversifying into other areas. It share price has tumbled by more than 30 per cent so far this year.

Shares in eBay slipped 87 cents, or 2.3 per cent, to $37.75 in pre-trade in New York today.

For more on eBay's purchase of Skype click here.

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