SAN ANTONIO — The broadband era began with the expectation that Internet connections were like buffets — all you can eat, 24 hours a day. But users are now being prodded to think about how much they’re consuming.


Here in South Texas, Time Warner Cable customers have been given the online equivalent of a scale in the bathroom, a “usage tracker” that adds up all the household’s Facebooking and YouTubing. Customers who sign up for a light plan of 5 gigabytes of broadband — that’s the equivalent of two high-definition movie downloads — are rewarded with a $5 discount each month if they don’t go over. If they do, they pay $1 for every additional gigabyte.


“We’re moving away from one-size-fits-all,” said Jon Gary Herrera, a Texas spokesman for the cable company, which now tends to call itself a broadband company instead.


Some of Time Warner Cable’s competitors are moving the same way, slowly but surely, toward tiers of pricing for higher speeds and bigger amounts of broadband at home, mimicking the wireless industry’s much-maligned pricing plans. The strategy, called usage-based billing, is advantageous for the companies that control the digital pipelines. But it may be detrimental for customers who are watching more and more video on the Web every month, as well as companies like Netflix that distribute it. Some fear that as customers become more aware of how much broadband they’re using each month, they’ll start to use less of it, and in that way, protect traditional forms of entertainment distribution and discourage new Internet services.


Executives at cable and broadband providers dispute that by saying it is in their interest to make broadband a must-have product. “The exploding growth of online video usage undercuts any argument that cable is standing in the way of this business,” said Brian Dietz, a spokesman for the National Cable and Telecommunications Association, the industry’s trade group.


But some government officials aren’t so sure. The Justice Department’s antitrust lawyers are conducting an investigation into the cable industry’s treatment of online video companies with an eye toward deterring anticompetitive behavior. Some analysts say the investigation could, perhaps counterintuitively, accelerate the move to usage-based billing.


As online video use soars, customers just want faster and better broadband service, and they complain (online, naturally) when Web pages or videos take too long to load. Kate Miller, a Time Warner Cable customer in Utica, N.Y., said her 2-year-old daughter Jane has already learned the word “buffering.”


“Elmo,” Ms. Miller said, “was never meant to buffer.”


There’s a clash between what users expect from broadband service and what is actually delivered to them, said Chris Balfe, the president of Glenn Beck’s media company, which created an online TV channel nearly a year ago. He has noticed sluggishness at home when trying to view YouTube videos. “As a broadband video provider it’s frustrating, but as a user it’s absolutely infuriating,” he said.


Usage-based billing is seen by some as a fairer alternative to broadband caps, a term most closely associated with Comcast, which had been enforcing a limit of 250 gigabytes per Internet customer per month. Although only a small minority of customers ever exceeded the cap, it became a lightning rod for competitors like Netflix, which accused Comcast of unfairly favoring its own services.


Comcast said this spring that it would start to test usage-based billing. “Our network is not an infinite resource, and it is expensive to expand it,” David L. Cohen, a Comcast executive, said at the time.


Along with news and entertainment, the futures of entire industries — commerce, health care and transportation — are being built atop a broadband foundation. Companies big and small are coming up with ways to get faster broadband to more people; many people believe that broadband speeds will inevitably improve as time goes on, just as computer chip speeds have.