The founder of the online giant is setting up a hugely ambitious news organisation. Will the combination of his tech savvy and commitment to investigative journalism offer a new media model?

By the time Pierre Omidyar was 31, he was, in his own words, not just regular rich but "ridiculous rich". With enough money to make an impact in pretty much any sphere he chooses, the eBay billionaire last week made a splash in an area that is increasingly attracting the attention of tech titans: news.

Journalist Glenn Greenwald announced that he was leaving the Guardian, where he has broken a series of stories on the National Security Agency, based on documents from whistleblower Edward Snowden. His new, as yet unnamed, venture will be a general news service backed by Omidyar. It will be the most hotly awaited news startup in years.

Omidyar's move comes just three months after Jeff Bezos, Amazon's founder, bought the Washington Post. Omidyar, too, had looked at the paper, he wrote in a blog post. "That process got me thinking about what kind of social impact could be created if a similar investment was made in something entirely new, built from the ground up. Something that I would be personally involved in outside of my other efforts as a philanthropist," he wrote.

The $250m he had earmarked for the Post will go into the venture that has already started hiring and whose investigative team will include Laura Poitras, the documentary maker who worked with Greenwald and the Guardian on the Snowden revelations, and Jeremy Scahill, the Nation journalist author and film-maker. Greenwald called it "a once-in-a-career dream journalistic opportunity that no journalist could possibly decline".

Omidyar is the only child of Iranian exiles. His physician father and linguist mother moved to Washington from Paris, where he was born, when he was six. He founded what would become eBay, the online market giant, in 1995. Three years later, the company went public and Omidyar was instantly vastly rich. Forbes magazine estimates his wealth at $8.5bn.

Unlike many of his billionaire contemporaries, Omidyar largely dropped off the tech radar. Some of the valley's biggest names owe their first fortunes to eBay after selling the PayPal payment system to the auction site. They have since gone on to fund the next set of tech titans. PayPal co-founder Elon Musk has backed grand plans, from Tesla's electric cars to SpaceX, a private space programme. Musk's former partner, Peter Thiel, has gone on to be one of the valley's most important investors and counts Facebook among the startups he funded. He now heads the Founders Fund, an investment firm that has its eyes on the cutting edge of tech, from robotics to biotechnology.

Omidyar and his Hawaii-born wife, Pam, have shown more interest in civics than social networks or space exploration. It's an attitude that has informed Omidyar's career; eBay was founded on a site he had set up to spread information about the ebola virus. He said he started it on the premise that "people are basically good" and the service is certainly one of the best demonstrations yet of how the web can build communities – allowing people across the world to trade their stuff, trusting strangers while rating their interactions. "Be you. Be cool," is the catchline on his Twitter profile.

The pair live in Hawaii and through their foundations have set about financing a series of citizen journalism and community-based projects that share common themes about informing communities and enabling debate.

Omidyar's philanthropic investments include Code For America, which links city governments with web developers and designers in an attempt to use tech to enable clearer communication between government and citizens. Omidyar has also been a supporter of the Sunlight Foundation, a non-profit organisation that gives people access to information on political candidates' donors and lobbying contacts.

The closest venture to his newest one is the Honolulu Civil Beat, founded in 2010, as a for-profit online news organisation covering Hawaii. The mission statements at the time of the launch were all a little wonky: Omidyar described the service as a "civic square for Hawaii". It was, he wrote, "about building a place where we can all... better understand our home".

The then editor, John Temple, announced the site would be launched without news and staffed by "reporter-hosts". The reality has proved less abstruse. "Civil Beat represented a return to fundamentals: shoe-leather reporting, filing Freedom of Information Act requests and examining public records, close coverage of government spending and campaign finance," former Civil Beat reporter Adrienne LaFrance wrote in a recent column for Reuters.

Omidyar's news initiatives so far have been focused and local. But over the summer, his ambitions broadened. Jay Rosen, media critic and NYU professor of journalism, said: "Something happened when he was asked to take a look at the Washington Post."

Rosen points to Omidyar's Twitter feed over the summer as evidence that he was becoming increasingly concerned about the plight of journalism in the US and the picture of the surveillance state that was being drawn out by the NSA revelations. A few weeks ago, he learned that Greenwald had been talking to Poitras and Scahill about a collaboration. "I think all these things just came together," said Rosen.

Media land is eagerly awaiting the debut of the service, not least because it comes at a time when some had been writing off the commercial viability of investigative journalism. Andrew Donohue, senior editor at the Centre for Investigative Reporting, said: "Pretty much every solution we have seen for investigative reporting over the last five years has been about non-profits. The argument has been that private money will not fund investigative reporting, so philanthropy has to step in." The new venture will aim to make money and reinvest that cash in journalism.

Rosen said Omidyar was clearly impressed by Greenwald's driven, partisan style but he believes a broader organisation is needed to help support it. "You need editors, you need other eyes on the stories, you need lawyers, ways to withstand the pressure. You need plane tickets!" he said.

Supporting investigative pieces with less controversial fare is hardly a new idea – not even in new media. Buzzfeed, the media company that made its name spotting pop culture trends and compiling addictively clickable lists, has been increasing its "serious" content. It broke the story of Greenwald's departure.

"Investigative journalism has always been subsidised. We just need to find new forms of subsidy," said Rosen.

And that may be Omidyar's key contribution – besides his cash. "When Bezos bought the Washington Post, here was someone who had made money from scratch, disrupting legacy businesses, sinking money into a legacy business. Why not take the money and start afresh?" said Donohue.

Omidyar's tech background and his focus on communities should prove an invaluable asset to the new company. "The way news systems work right now is still pretty primitive," said Rosen. People who are avidly following a story get the same content as people who just want a summary. There is a lot of talk about personalisation but not a lot of good examples.

At the same time, the forms of journalism that people want are changing. Journalist "brands" are common on TV and in areas such as sport and entertainment. Donohue said it was harder to establish those brands with investigative journalism, where the lead time between stories is much longer. But Greenwald has developed a huge online following and a style that fuses comment and news that appeals to readers looking to drill down on the topics that interest them.

After interviewing Omidyar, Rosen wrote: "Part of the reason he thinks he can succeed with a general news product, where there is a lot of competition, is by finding the proper midpoint between voicey blogging and traditional journalism, in which the best of both are combined."

Omidyar's move sends a significant signal. Far from killing investigative journalism, as many naysayers have predicted, the new media landscape is creating more ways to fund it. "People who say things are over should be over," said Rosen.