Meanwhile, IBM's shares sailed north as the stock became one of the favoured plays on the new hot industry on the horizon: the cloud.

Yet as we were reminded last week with IBM's jolting earnings downgrade, following the pack into what Michael Lewis calls the "new new thing" is rife with uncertainty.

"We saw a marked slowdown in September in client buying behaviour, and our results also point to the unprecedented pace of change in our industry," IBM chairman Ginni Rometty said during the results announcement.

Another problem with growth industries is that they are very crowded: no one can risk staying on the sidelines.

In the case of cloud services, everyone from Hewlett-Packard and Dell to Apple and IBM know they need to be there, and they are. Many smaller start-ups are also focused on this latest niche of the digital age.

Inversely, one good thing about maturing industries is that the competition starts to thin out.

Imagine trying to raise funds to start a personal computer business these days? The trend is that such businesses are closing down, not starting up. The number of computer brands out there has fallen from more than 400 since the peak in 2009 to fewer than 300.

Competitors are throwing in the towel for good reason. The business is extremely difficult, with sales falling in recent years because of tablets and smartphones.

Personal computers in particular look like the dodo bird of the digital universe.

But as the field clears, the remaining players can find themselves with sturdy franchises. And players large enough to enjoy the efficiencies of scale can spin cash from this low-margin franchise.

"In the end, the business is becoming 'easier' for those still around and willing to continue participating in the industry," says Alberto Moel of Bernstein Research.

He thinks Lenovo and Taiwan's Asustek are two beneficiaries of the trend, and will enjoy enhanced market scope and pricing power as the personal computer landscape consolidates.

Average selling prices are starting to stabilise in part because many customers are "replacement buyers" who know they need a personal computer; industry players feel less compelled to offer price discounts to old customers.

And while many analysts remain concerned about Lenovo's latest round of acquisitions (from Motorola, and, again, from IBM), in recent years, the firm has consistently beaten analyst expectations.

This is not to write off IBM's strategy of focusing on the future.

The company has positioned itself as a key player in an industry that is growing fast: cloud computing had US$91 billion in sales in 2011 and is forecast by the consultancy Garner to grow to more than US$200 billion by 2016.

But Lenovo's successes in recent years are a reminder that generating cash from mature industries can sometimes be easier than burning cash investing in new ones.

Walmart is perhaps the quintessential example of this principle.

Here was an unexciting and old-world industry if one ever saw it when Sam Walton entered: selling underwear and frying pans to penny-pinching lower-end consumers.

But by creating scale and improving efficiency, Walmart dominated the industry and turned itself into one of the largest companies in the world.

Like Walmart, Lenovo has relied on scale to triumph in an ageing industry. The computer firm is top brand in a number of emerging markets, most notably China's.

"I thought for a long time that Lenovo was just a bunch of opportunistic overreachers far surer of their ability than the reality. I've come to conclude that they are smarter than that," says Moel. "I like to think Lenovo is very good at turning somebody else's trash into treasure."