VoIP service Skype said it recently reached the 15 million concurrent user mark, claiming 405 million Skype users in all. But what's even more impressive is how quickly the service is growing. Skype estimates it adds 380,000 new users each day. To put that number into perspective, Ross Storey, Managing Editor at Fairfax Business Media, points out that over a 12 day period, the number of users Skype adds is equivalent to the population of Singapore.

Skype announced the figures in Signapore during the launch of the new Skype 4.0 software, which the company calls "the most exciting and fundamental change to Skype's software in the company's history." Even more exciting for the company is recording the eighth consecutive quarter of profit, in which Skype earned $45 million in Q4 2008. This is thanks in large part to a third of its registered subscribers using the service for business purposes.

"In this type of environment people are looking for cost savings wherever they can find them, they are looking to 'recession-proof' their businesses," said Dan Neary, Skype's new VP and GM. "hey don't want to fly from A to B, they want to do video-conferencing. More and more, this offering is becoming applicable for people in business."

Last month, a rumor surfaced suggested Ebay was shopping around its Skype service, showing particular interest in selling to Google. If Skype keeps up these kinds of numbers, it's hard to imagine Google, or anyone else, not being interested.