Loss of market share could have severe consequences for companies with high debt levels, like Cablevision and Charter Communications, which could find their ability to pay off debt impaired by a drop in cash flow, Mr. Bourkoff said. Comcast, however, has demonstrated its ability to acquire an increasing share of the high-speed data pie, several analysts said. On Thursday, when the company reported earnings for the first quarter, executives said it had added 417,000 high-speed Internet customers, up 52 percent from the period last year. Comcast has also begun to stem subscriber losses at the AT&T cable systems it acquired last year. Comcast has particular appeal because, in the near term, it is not betting as heavily as its rivals on revenue growth to generate improved earnings. It projects revenue growth of 10 percent this year, compared with a projection of about 15 percent at Cox, the nation's fourth-largest cable operator.