Two years ago the big thing was VoIP, telephone over the internet. The new big thing is TV over the internet, and it's a tempting big new thing indeed, promising to represent a real challenge to cable.

At the least, it stands to force down the high price consumers pay to watch television. And as a competing distribution stream, IPTV could also usher in a flood of new, innovative programming choices.

The question is when? Technologies on the horizon have a way of staying on the horizon, defying their promoters' promises of sweeping through the marketplace any minute now.

The answer appears to be: sooner than you might think, and easily within several years, according to a new study.

Though still in its infancy, IPTV already has some 300 trials behind it worldwide, and services are up and running in some countries, despite some remaining bugs.

“It’s still very early in the game. The technology is very new, and the operators are still trying to figure out what it will be that will attract people to the offer,” says Denis McCauley, editor of a report on IPTV. “But it will become a viable competitor.” McCauley is director of global technology research for the Economist Intelligence Unit, which did the study with Accenture, a self-described global management consulting and technology services company.

Within a year, distributors should be able to offer content to rival cable and traditional TV. McCauley figures that within one to two years, any remaining bugs with the technology will be worked out and the quality will be as good as cable's.

Driving the challenge will be telephone companies, which with revenues from traditional voice services slumping are now pushing into broadband with a range of services. IPTV will enable them to offer so-called triple-play service of voice, internet and entertainment to lock in customers the way the cable companies are now doing with their triple-play offerings.

“The ability to offer IPTV has given the telcos the chance to offer this triple-play of voice, internet and media services, and thereby try to claw back ground that they have lost to the cable companies, primarily,” says McCauley.

Still, significant IPTV revenue could be years out for the telecoms, the Accenture study found. It was based on a survey of 302 high-level executives at telecom, broadcasting and media companies worldwide.

In fact, only 4 percent of those surveyed are very confident that IPTV will generate significant revenue for their industry in the coming year. Looking three years out 34 percent strongly believe that IPTV will be generating significant revenue, with 57 percent somewhat confident.

“If you are looking out five to seven years, I would guess that IPTV would maybe not be an equal competitor in terms of number of subscribers with cable, because IPTV is not cheap, but it is likely to be a viable competitor,” he says.

The key revenue generation area for IPTV over the next three years is seen by the respondents as being video on demand. Some 19 percent of respondents believed that VOD would be the most significant money-spinner in the next three years.

As for advertising, it managed only sixth place on the list of the anticipated revenue generators, with only 6 percent believing it would be the most significant form of revenue in three years' time.

But McCauley suspects that advertising will be more important than the  survey would imply. “I’m not going to say that it will be the dominant source of revenue, but I think that it will be a more important source of revenue than our respondents said.”

Meanwhile, in online ratings for the week ended July 23, the top four parent companies remained the same. Microsoft was No. 1, followed by Yahoo, Time Warner, and Google. News Corp. jumped back above eBay for the fifth place spot by about 1,300 unique visitors, according to Nielsen//NetRatings. Top five brands remained the same: Yahoo, Google, MSN/Windows Live, Microsoft and AOL.

GUS Plc once again retained the top spot among advertisers, delivering 7.27 million impressions. Verizon took the second-place spot with a distant 1.71 million impressions, followed by NexTag, United Online and Netflix.

Sessions held steady at 16, and domains visited per person fell one from last week to 37. Average PC time per person fell about 3 percent from last week to 15 hours, 59 minutes, and 36 seconds.