On the other hand Yahoo! might be doing no more than engaging in a spirited rear-guard action. It might succeed in protecting its franchise for a time. But can anything stop Google? All competitors must feel as if the challenge is equivalent to pushing water uphill using nothing but bare hands.

Advertising income, in one form or another, is the life blood relied on by both Google and Yahoo!. That said, the two depend on different strains of the form. Google earns its crust largely by levying a small toll as internet traffic passes through its site. The Yahoo! model charges advertisers in a more conventional way for the privilege of putting an image in front of a set of consumers.

The Yahoo!/eBay venture may be profitably sustainable because it follows a distinctly different path to Google. Google professes to an ambition of being an “anti-portal”. Unlike Yahoo! and eBay, whose primary aim is to get people to visit its website, Google bounces users off its internet domain as soon as it can.

You may argue about which strategy is the most promising. But it is surely likely that both constitute income streams that can grow.

And maybe they will. The link with eBay represents a sensible step forward because those pursuing eBay auctions represent something akin to a captive audience. Moreover, most visitors to eBay auction sites are engaging in a financial transaction or are preparing to engage in some sort of bargaining. They are, in other words, an audience with money and they are the best sort as far as advertisers are concerned.

But the danger for Yahoo! is that the psychology of internet use works to promote a single dominant force. It may be inevitable that the winner takes all and, on current form, Google is that winner. Meanwhile, Google may decide to adapt its click-through model. It might be wedded to it for the moment but content is being appended to its website. The recently rolled out Google Finance moves some way in that direction, as does the Google Earth product. Both could sustain advertising of the conventional display variety.

EBay, it is only fair to add, may have less to fear from the winner-takes-all analysis. Users of the internet may be prepared to allow only one winner to emerge in any particular internet discipline. But if web users look for different functions — and they do — a series of winners may emerge.

Google may take the crown when it comes to internet searching. eBay has already won global pre-eminence in online auctions. As for Yahoo!, the prospects are less clear.

BAA safer

PLUNGING share prices ought in principle to make life easier for cash bidders. But it is not working out that way at BAA. The airport operator is looking safer by the minute from the Ferrovial consortium’s 810p-a-share bid or even from a bigger private equity offer.

As befits a company headed by Marcus Agius, a career corporate finance specialist, BAA’s defence is robust and convincing. With a nod to steelmaker Arcelor, it combines a substantial return of capital with a confidence-building pledge to jack the dividend up and to keep it rising from this new base.

Mr Agius’s attempt to value the business as the sum of its parts is more crucial but makes a good case for a premium utility rating worth 940p a share. The assets are irreplaceable and the CAA’s drive to expand capacity and BAA’s record of delivery point to growth.

Times Recommends

• B&B shareholders forced into funding rescue
• John Lewis department store sales plunge 8.3%
• Families turn to credit to cover mortgage bills