US consumers using an expanding array of broadband services, including movie downloads, video games, online backup, and streaming audio and video, are flooding the nation's broadband pipes with data--and it could cost them.

Consumer advocates say that it's only a matter of time before average high-speed Internet users get slapped with the label "hog."

Craig Aaron, spokesperson for SavetheInternet.com, worries that Internet users may soon be charged extra for using "too much" bandwidth or cut off from using some bandwidth-hungry software applications.

Bandwidth demands in the US have been doubling each year for some time, according to Tom Donnelly, cofounder of Sandvine, a network management firm. As this trend continues, Donnelly says, it puts pressure on ISPs and on applications such as file-sharing software and streaming multimedia content, giving ISPs an incentive to clamp down on heavy bandwidth users.

Major broadband ISPs shrug off criticism that their networks can't handle the increased demand for bandwidth. "We've been successfully delivering broadband services to our customers for 10 years, and that's not going to change anytime soon," says Mitch Bowling, senior vice president and general manager for Comcast's high-speed Internet group.

Time Warner, Charter Communications, Cox Communications, and other ISPs echo those sentiments. "Our network is extremely robust and [bandwidth] issues aren't a problem for us," says Jim Mailla, spokesperson for Optimum Online, a Charter Communications company.

Putting the brakes on bandwidth hogs

Despite the rosy picture painted by ISPs, some service providers are already clamping down on bandwidth hogs. Others are experimenting with payment plans (such as tiered pricing) that raise the cost to consumers of excessive bandwidth use.

Analysts say that these moves indicate increasing pressure on broadband systems due to the volume of demand, and note that leading ISPs are moving quickly to avert bandwidth bottlenecks, as well as to forgo spending billions to upgrade aging networks.

For instance, Comcast has been tinkering with the way file-sharing software works on its network, slowing transfer speeds of data used by applications such as BitTorrent. Comcast has also been giving the heave-ho to customers who use the Internet most heavily, explaining that certain individual downloaders are using as much bandwidth as some of its business customers.

Comcast spokesperson Charlie Douglas explains that a single customer who uses disproportionately more bandwidth than his or her neighbors can slow down the Internet for everyone on the block. Comcast has faced a user uproar for manipulating the way file-sharing programs work and for introducing bandwidth caps on individual accounts without identifying what those caps are.

Time Warner Cable's approach

Time Warner Cable is experimenting with managing bandwidth by billing its customers, not at a flat monthly rate, but on the basis of how much bandwidth each customer uses. The cable company is rolling out a trial version of a consumption-based billing system in Texas later this year. "We have more than enough bandwidth, but we are looking to the future," says Alex Dudley, spokesperson for Time Warner Cable.

Under the new billing scheme, customers who exceed their monthly bandwidth allotment risk incurring an overage charge. A spokesperson says that the billing scheme isn't in place yet, so the company doesn't yet have any hard numbers available regarding these charges.

Cox Communications says that it now imposes "monthly consumption caps" on its customers and reserves the right to "suspend" account holders who use more than their allotted bandwidth. The company outlines these policies on its Web site.

If Cox users consistently exceed their bandwidth limits, Cox either sends them an e-mail or calls to urge them to reduce bandwidth consumption or upgrade to a higher tier of service, says David Deliman, a Cox spokesperson. Cox wouldn't say whether the company has ever ousted a customer.

AT&T's CEO Randall Stephenson has said publicly that he has considered blocking pirated content from the AT&T network. Big Champagne, a market research firm that tracks file-sharing sites, estimates that peer-to-peer traffic accounts for more than half of all Internet traffic.