It’s been a great week for the online journalism business. Billionaire eBay founder Pierre Omidyar committed $250 million to a general-interest news site anchored by investigative reporter Glenn Greenwald. Venture capitalists, meanwhile, bestowed $34 million to Vox Media, publisher of technology and sports sites.

Both deals come just a couple of months after Jeff Bezos bought the Washington Post for $250 million. From a funding perspective, at least, it certainly looks like content is back. And that should be heartening to people who support uncompromising, relentless, and controversial journalism as practiced by the likes of Greenwald.

It’s hard not to feel optimistic when a billionaire like Omidyar says he wants plow hundreds of millions of dollars into supporting “independent journalists in a way that leverages their work to the greatest extent possible ... to convert mainstream readers into engaged citizens.” Or when Bezos says he wants to bring a new “golden era” to a storied newspaper.

But you don’t build a sustainable industry resurgence on the unilateral whims of two billionaires or on a few drops from the firehose of venture capital, which remains squarely aimed not at content but at core Silicon Valley technology like online services, social networks, mobile software, and hardware.

It’s worth keeping in mind that content became a financial sinkhole the last time boomtime investors allowed themselves to get starry-eyed about words. Fourteen years after its IPO, Salon.com is still in business, but with accumulated losses of $116.5 million. Slate, a contemporary of Salon’s, cost Microsoft a reported $20 million before it was sold to the Washington Post Company. (Bezos apparently passed on buying it along with the Post.) And – full disclosure – the publication you’re reading was forced to cancel its own planned IPO back in the 1990s tech boom.

Some content plays, like CNET, did make it profitably through that boom, but the woes of other news operations made it clear the internet wasn’t any safe harbor for the historically dicey media business. And online journalism remain risky; AOL is still struggling to turn its roll-up of sites like the Huffington Post and TechCrunch into a real business.

Omidyar, at least, seems to have begun auspiciously, judging from NYU professor Jay Rosen’s excellent rundown of his strategy: He’s avoided entangling himself in an existing business with a declining print operation; he’s committed a big budget up front, giving his as-yet unnamed publication an air of invincibility; and he’s already pledged to diversify beyond the political and civic affairs coverage for which Greenwald is known, which should make advertisers happy (as the Huffington Post learned, advertisers avoid political content). But even the best laid plans – and the most dogged journalists – are no guarantee of success in the news business. Not 100 years ago, not 10 years ago, and certainly not today.