Comcast, the Philadelphia cable-television giant, must be the only media powerhouse that owes its start to beltless pants. Ralph Roberts was running a belt-and-cufflinks business when he saw something alarming: an ad for slacks that didn't need a belt to stay up. Roberts already knew cuff links were history. Fleeing the beltless revolution, he sold the company and bought a cable franchise in Tupelo, Miss., in 1963. During the next few decades, he and his son Brian built that tiny system into the nation's third-largest cable-TV company.
Or the largest. How that story ends will be determined by AT&T;'s answer to...