Spanish startup FON has inked a deal with U.K. broadband provider British Telecom to create what they claim will be the world’s largest Wi-Fi community, potentially giving BT’s 3 million broadband customers access at no additional charge to FON’s network of roughly 190,000 Wi-Fi access points.

In return, BT subscribers who sign up for the scheme will share a small portion of their connection by opening a separate secure channel on their wireless router for other FON members to use. Non-members can also access the FON network, at a price – FON takes care of the billing and the user sharing a portion of his connection gets a cut of the proceeds. Of course, users may fear getting penalized for letting others use up their entire monthly data allowance. BT, however, says any data the guest downloads won't count towards the owner's usage allowance.

As part of the deal, BT also bought a stake in the Spanish company, although details of the deal were not disclosed. Other investors in FON include Google, Skype, Index Ventures and Sequoia Capital. The move gives BT a quick jump in its public access Wi-Fi coverage at a minimal cost, while FON gets the exposure and credibility it needs to encourage more people to join.