So he's taking another crack at it, going after Monster, Career Builder and similar commercial job sites. Warren is starting a nonprofit job listing system that could lower the costs that employers pay to list positions and make the process easier and more fruitful for applicants.
He has the enthusiastic backing of hundreds of large companies, including IBM Corp., American Express, AT&T Inc. and Johnson & Johnson, the kinds of employers that spend hundreds of thousands of dollars a year searching for new talent.
"This is probably the most significant play that I've seen ... since the invention of the online job board," said Joshua Akers, vice president of RecruitingBlogs.com, a social networking site for human resources professionals.
The commercial rivals say they are ready for new competition. "We remain confident that we're one of the most cost-effective sources of hiring for recruiters today," said Monster spokesman Matt Henson.
Warren, 68, says that those commercial sites charge employers so much to list openings that the companies don't post all their jobs - leaving potential applicants unaware of opportunities. Warren also believes that the sites push too much advertising on jobseekers and include too many "work at home" scam jobs.
Meanwhile, employers want ways to have a direct relationship with jobseekers. Many say they prefer resumes that are tailored to the positions they're trying to fill, not a generic resume posted online. As the ranks of the unemployed have doubled to roughly 15 million, recruiters say the response to jobs they post on the boards has gotten overwhelming.
The solution that Warren hopes to launch next month is being hatched by the DirectEmployers Association, a group formed by more than 500 large companies. Warren is executive director.
The association's plan calls for companies to list jobs under the Internet's ".jobs" domain name - similar to ".com" or ".edu" - to better organize job listings on the Web. For instance, someone can visit ATT.jobs to see all the listings at that company.
DirectEmployers' software will automatically code such listings to make them easily searchable by city or occupation. The association also will sort the listings in as many as 30,000 regional ".job" Web addresses it hopes to begin rolling out in March, such as "atlanta.jobs." That will help people search for jobs in specific places. The group hopes to add thousands of occupational domain names, such as "engineer.jobs," later this year.
Companies that belong to the association pay a $15,000 annual membership fee and will receive prominent placement on the ".jobs" Web sites. Smaller companies can purchase a ".jobs" domain name for about $125 a year and then post jobs for free. They can also work through their state employment agencies, which post jobs online at no charge.
At those prices, the new ".jobs" system could be another online innovation that undercuts what currently exists - much as the invention of job boards themselves undermined newspaper help-wanted ads.
Monster.com's basic rate is $395 per job posting, though it offers volume discounts. Companies also pay to search the resumes that applicants have posted. (Jobseekers can access the sites for free.) Considering that some Fortune 500 companies hire thousands of workers a year, even in tough times, the cost of listing all their open jobs can approach $1 million.
One company planning to participate in Warren's new system is Newell Rubbermaid Inc. Mike Rickheim, vice president for global talent acquisition at the consumer products maker, still plans to use commercial job boards to post some positions, but that "will likely continue to trend downward" once the new system is running, he said.
Still, the commercial job boards say they are ready. Henson at Monster.com said the company's recent acquisition of Yahoo's HotJobs gives it the world's largest online jobs and resume databases. Monster has developed new search technology for its site that makes it easier and quicker for employers to sift through resumes and find the most relevant ones, he said.
Career Builder, which is owned by Microsoft Corp. and media companies Gannett Co., McClatchy Co. and Tribune Co., didn't return several calls seeking comment. The company says it lists 1 million jobs and 31 million resumes. Monster wouldn't provide equivalent figures.
Warren started Online Career Center, the first online job board, in 1992. It was bought by TMP Worldwide in 1995, then combined with Monster.com in 1999. Warren says he left Monster that year after the then-chairman of the company set a goal of raising the price of an online help-wanted ad to $1,000.
"I just did not agree with that philosophy," he said. "I thought the Internet was more open than that and I thought the price of ads would be going down in the future and that's exactly what's happening," he said.
Still, Warren insists he isn't seeking revenge against Monster or any other company. "I wouldn't know anyone at Monster if I walked in the door today," he said.
Instead, he said, his goal to help more people get back to work faster.
That might be a stretch, according to David Autor, a labor economist at the Massachusetts Institute of Technology. Efficiently matching applicants and companies is only a small part of the problem when it comes to filling jobs. An employer still has to decide who is the best fit.
"The challenge for employers has not changed in the Internet age," he said. "It's hard to figure out who is the right person to hire."