The advent of DSL and cable modems gave rise to a slew of popular web services, produced multibillion dollar companies and reshaped consumers' daily lives – all with relatively wimpy "broadband" connections that top out at a mere 3 to 6 megabits per second (Mbps).

Now two of the largest ISPs in the United States are hoping to kick off yet another broadband renaissance, this time with home connections that promise to reach 50-100 Mbps, enabling a slew of high-definition content, better-quality video-sharing sites and even 3-D video. Call it Broadband 2.0.

Experts say this increased bandwidth – when it becomes widely available – will have a profound effect on everything from our social interactions on the web to the way we consume media.

"The YouTube philosophy is really the primary motivator here," says Connie Chang-Hasnain, a professor of electrical engineering at the University of California at Berkeley and expert in broadband communications. "Even grandmas post things on YouTube. But, right now, the resolution is terrible and there are some very predefined limits due to bandwidth."

All of that will change with 50 Mbps download speeds, she said, and by simply improving the sound and video quality of video streaming sites, you can dramatically change how a society learns, teaches and communicates.

"Basically, people are going to do a lot of the things they normally do today, but in a better, more satisfying, way," says Crick Waters, co-founder of Ribbit, a Silicon Valley company that sells an internet-based telephony platform.

Waters says that first and foremost, we can expect everything to go high-definition: We'll download HD movies from Netflix, upload HD content to YouTube, and watch more sophisticated HD content on our televisions. The added bandwidth may even spur development of extra goodies, like stereoscopic 3-D video and high-fidelity audio.

"Believe me, the minute someone puts the pipes out there, people will find a way to use them," Waters says.

While the technologies they use differ, Comcast and Verizon have both started offering ultra-high-bandwidth services to select customers that are as much as 25 times faster than today's average broadband speed of 4.8 Mbps, according to the Information Technology and Innovation Foundation. Comcast's new "extreme high-speed internet service" uses the latest version of cable modem technology, while Verizon's FiOS service delivers the internet to your home via optical fibers.

Both services are currently available only in relatively limited geographic areas. Earlier this month, Comcast started offering a service to some Minneapolis/St. Paul residents that features download speeds of 50 Mbps for a hefty $150 a month. During his CES keynote in January, Comcast CEO Brian Roberts said his company plans to expand this new service in 20 percent of the area it serves by the end of the year, as well as offer speeds in excess of 100 Mbps in two years.

Verizon's FiOS has a yearlong head start on Comcast's service, and Verizon currently offers it in parts of 17 states. Verizon said it will offer its fiber-to-the-home services to more than 18 million people – half of the geographic area it now serves – by 2010.

Obstacles remain for both companies. Deploying the services widely will take time – and lots of money. And even if the companies sink their capital into second-generation broadband networks, there's the risk that customers won't pony up for them unless there is compelling content to go along with that bandwidth.

"If you put a 60 Mbps service out there, people are also going to want to have services associated with it. Yet no one is going to create those services unless the 60 Mbps is there," Water says.That hesitation may not last long, because consumers always find ways to use up whatever bandwidth is available – and then some – says Rudolf van der Berg, the author of a recent study on the future of fiber networks (.pdf).

Van der Berg predicts that the average household will need 50 Mbps download speeds (and 10-50 Mbps upload speeds) between 2010 and 2020. And even that might not be enough: "Every new advance … has enabled new services over the available bandwidth," he says.

In the end, the more bandwidth that becomes available to customers, the easier it becomes to develop new content offerings.

For example, Verizon suggests that its services might enable companies to offer not just HD programming, but multiple views of sporting events, wide-angle views comparable to an Imax experience, and ultra-large screens (beyond 100 inches). Eventually, the company suggests, we'll clamor for Super HD (2160 vertical lines) and Ultra HD (4320 vertical lines) television broadcasts, which could require as much as 256-480 Mbps of bandwidth.

In other words, whatever bandwidth you've got now is never going to be enough. Broadband 3.0, anyone?