Life without a cable box in millions of homes would be excruciating, devastating and empty.

How else would you expect the cable companies to feel if the Internet -- after plundering the music industry, Hollywood and newspapers -- becomes the dominant delivery system for television programming in the United States?

It could happen.

"There's no reason why the Internet cannot replace cable or satellite or even OTA [over-the-air] transmission of content," says Edward Woo, an Internet and digital media analyst for Wedbush Morgan Securities in Los Angeles. "When the Internet as a TV platform really takes off, it will strain the cable companies' current business model."

Newspapers were the first to falter. Now it's the cable companies' turn to withstand or wither. Last month, in an unprecedented collaboration, Comcast and Time Warner announced a deal that would allow Comcast subscribers to watch Time Warner's cable networks -- TBS and TNT would be the first -- via the Internet.

That move could represent the beginning of a new TV reality, the possibility of buying only the programming you want -- for example CNN, ESPN, A&E and HBO -- from various vendors without all the filler and expense of cable bundles. More likely, it's a cable plan to preserve those bundles and audience dominance.

"I have a theory that consumers don't want multiple vendors," says Russ Crupnick, an entertainment analyst for the NPD Group in Port Washington, N.Y.

People "already have a relationship with Verizon, T-Mobile or AT&T. We have a billing relationship with cable," he says. "That's a huge relationship."

For that reason, this could be cable's game to lose. Cable has the built-in audience, the delivery system (the ubiquitous set-top box) and the potential for vast video-on-demand offerings.

But cable companies might find, just as newspapers did, that the Internet is a road paved with pennies. Once people get something free, they don't like paying for it. The music industry's pay-per-song model worked only after a legal crackdown on unauthorized sharing of free music downloads. Newspapers, even when teetering on extinction, still haven't figured out if a payment system is a risk worth taking.

Cable, likewise, must ask where the money will come from. A network show on Hulu, an online outpost of free TV programming run by NBC and Fox, might generate one-third of the advertising revenue of a network broadcast. Nielsen, whose ratings help establish ad rates for broadcast television, still has not found a way to quantify Internet or mobile use.

Movies and TV programs now come streaming into homes from all directions: gaming consoles, Blu-ray players, set-top boxes, even from the Internet's grandest shopping mall, Amazon.com. Eventually, the new generation of Internet-enabled HDTVs might eliminate all these set-top links to the Web.