Company name: Skype
Where it's based: Luxembourg, France
When it was founded: 2003
What year it was a Fierce 15: 2005

Why it was a Fierce 15: Leveraging peer-to-peer technology to power a free PC-to-PC VoIP service, Skype attracted nearly 10 million users in its first year of operation. Since then, the company expanded to include prepaid voice. The company also added support for traditional phones and mobile devices, allowing cell phone Internet calling from WiFi hotspots. Click here for more.

What has happened since it was awarded the Fierce 15: Skype was acquired in September 2005 by eBay in a deal that ballooned to $2.6 billion with performance incentive payments to Skype's cofounders. Despite Skype's more than 450 million users and estimated 2009 revenue of $600 million, eBay could not find synergies with the company, and announced it will sell a 65 percent stake in its Skype communications unit to a group of private investors led by Silicon Valley private equity firm Silver Lake Partners. The investors will pay $1.9 billion for a majority interest in the VoIP service, including a $125 million loan from eBay. The deal values Skype at $2.75 billion.