As part of a plan to offer free WiFi to its customers BT ( NYSE: BT ) has taken a financial stake in Spanish WiFi startup FON, although the size of the stake and the amount paid weren’t disclosed. “BT’s three million plus Total Broadband customers will be able to join the FON WiFi network, which already provides more than 190,000 hotspots worldwide. By doing so, BT’s customers will effectively turn part of their home WiFi system into a public network, which others can then access, reports DJ Newswire. There’s a suggestion this will create the world’s largest WiFi community… One of the reasons for the deal is that BT hopes to expand its Fusion service, which lets customers roam between fixed-line, mobile and wireless networks. Release.