(Fortune Magazine) -- Niklas Zennstrom is a populist Web hero. The 40-year-old Swede has twice co-founded companies that rattled powerful industries by giving away important things to consumers.

Skype is shaking the telecom industry with free phone calls, and before that Kazaa, his maverick music-sharing company, sent shivers through the entertainment business. So keep an eye on a Madrid wireless Internet startup Zennstrom is helping to run called FON, which could upend both the Internet and the mobile-phone industries.

FON is building an international network of free Wi-Fi by enticing people with home Wi-Fi service to share access with fellow "foneros" when anyone in the FON club is within range.

"I'm a great believer in sharing resources to create a virtual-access network," says Zennstrom, an active board member. FON's CEO, 46-year-old serial entrepreneur Martin Varsavsky, shares that vision. "We are a user-generated infrastructure," he says, "not telco-generated."