Old media companies spent much of last year having a mid-life crisis. Made to feel dull and grey, they willingly gave their name to younger, funkier, online rivals in a vaguely desperate attempt to look cool.

Now, the morning after the internet party of the night before, many of these grey-beards are suddenly seeing their once-cocky adolescent partners in a whole new light. Why put up with all the whining and the blemishes when time, money and reputation now seem much more attractive?

Few old media companies underline this new confidence in maturity as much as the Old Grey Lady. The New York Times and TheStreet.com, in a little-noticed sidebar to the news that a financial website was closing its UK operations and sacking 40 people in the US, announced that their joint newsroom was to be shuttered.

The collapse of this 18-month-old experiment marks a new chapter in the development of online news operations. The partnership between the New York Times and TheStreet.com was one of the earliest efforts to amalgamate the best of the new and the old in the rush online. The newspaper wanted the pizzazz and speed of the newcomer, while the website craved more credibility.

In stilted comments made at the time of the announcement, both companies said they had learned a lot from each other and had ended their relationship by mutual consent. The New York Times still has a 5.7% stake in TheStreet.com.

Money was not the cause of the split, in spite of signs of retrenchment on both sides. Problems arose because of editorial rather than financial values: the New York Times felt it no longer needed to be told how to write fast business news for its online readers by an outfit that did not share its values or ideals.

Bill Keller, the managing editor of the newspaper, says that the world now recognises that inventiveness and energy are no longer the province of the new. "This has definitely been a learning experience," he says of the joint newsroom, before adding: "It has underscored that we old media folk can actually do new media ourselves. We don't have to do it in partnership with a dot.com."

The seven journalists of the joint newsroom who sat in the Wall Street offices of TheStreet.com were pulled in different directions by the two partners. Simply put, one wanted fast and furious news to use for investors, while the other wanted considered exclusives and analysis. Neither side was ultimately happy with what was produced.

Executives at TheStreet.com had hoped to be able to work more closely with their colleagues at the NYT, but it was not to be.

Research into the readership of both organisations could have highlighted the gulf between them. TheStreet.com provides waves of instant financial news and aggressive analysis in a format prized by market professionals and investors. Readers of the New York Times have more general but perhaps more sophisticated interests.

Keller highlighted the gulf between the two when he compared the ambitions of TheStreet.com with the financial equivalent of a sweatshop. "TheStreet.com conceived of [the joint venture] as a boiler-room, while we conceived of it more as a newsroom."

The newspaper intends to appoint two or three of the joint newsroom journalists to something it calls a continuous newsdesk, an eight-strong operation which files online stories. These journalists are all fully fledged members of NYT staff, unlike those in the joint newsroom. The continuous newsdesk, established 18 months ago, was also an experiment. Set up in the heart of the NYT's own newsroom, it was one that worked, however.

The collapse of one of the earliest affairs between old and new media companies raises questions for other partnerships. Few, however, are showing any outward signs of such a culture clash.

Indeed, just a few days before, FTMarketwatch.com, a joint venture between the Financial Times and Marketwatch, a US website, announced its intention to expand into Germany. Both the FT and CBS, the US television network, own significant stakes in Marketwatch, although the transatlantic ventures are managed separately.

Other partnerships, notably that between the Washington Post and MSNBC.com, are sharing editorial rather than financial resources. The situation is fluid, with many media companies still toying with the go-it-alone versus the alliance route in the US. Larry Kramer, the chief executive of Marketwatch.com, says: "Everybody is trying to figure out how to get to where they want to be and how best to manage their business in a changing climate."

For the New York Times, where they want to be for now is left alone to their own considerable resources.