July 9 — Broadband providers are cracking down on popular Wi-Fi networks, threatening to cut service to customers who set up the inexpensive wireless systems and allow others to freely tap into their Internet access. Time Warner Cable of New York City has given 10 customers less than a week to stop using their accounts to provide a wireless local area network available to anyone within 300 feet. The letters are just an initial volley; Time Warner expects to send additional letters, while AT&T Broadband also is preparing similar letters for some of its customers. The crackdown is reminiscent of...