There has not been a lot of consensus in the bizarre, prolonged battle for control of Yahoo but all the participants are united in one belief: do not trust the other guy.

Carl Icahn, the activist investor, wants to kick out Jerry Yang, Yahoo's co-founder and chief executive, and Yahoo's board. Steve Ballmer, Microsoft's chief executive, has no interest in Yahoo unless Mr Yang is no longer around to cause trouble. For his part, Mr Yang told The Wall Street Journal this week that: "To trust Mr Icahn and his board is a really bad choice."

The shareholders will decide on the matter at the annual meeting on August 1, when they vote on whether to take Mr Icahn's Yahoo board slate or stay loyal to Mr Yang. My advice is to go with Mr Icahn and Microsoft, if it will renew its full bid, rather than trust Mr Yang to fix Yahoo.

Mr Yang co-founded Yahoo in 1994 as a web directory and was "Chief Yahoo" - an intentionally mysterious role - while Terry Semel was chief executive. He has run it since last year, when Mr Semel was eased out. So he bears ultimate and proximate responsibility for the fact that Yahoo is, frankly, a bit of a mess.

From the start, Yahoo has been more of a Gestalt, or a shape, than a company. When pledging loyalty, executives talk of "bleeding purple", its signature colour. Microsoft makes software, Google does search, Facebook is a social network. Yahoo is purple and has an exclamation mark.

When asked at a Journal conference last month what Yahoo was, Mr Yang replied: "We want you to start your day at Yahoo." You could equally say that of a shower, a café or a train. The thing that Yahoo most reminds me of, however, is a newspaper.

Like a newspaper, it has all sorts of bits and pieces combined into one package. A paper has news, financial information, sports results, personal ads, puzzles etc. Yahoo has all these as well as search, e-mail, photo storage and a bunch of other services.

This brings Yahoo plenty of traffic - it has 500m users - and, in the years when internet companies were valued on "eyeballs" rather than revenue, it also brought an extremely high valuation. Its market capitalisation hit $149bn at the end of 1999.

It has since fallen to about $33bn (€21bn, £16.7bn), while Microsoft's February bid valued it at $44.6bn. Google, although its value has fallen from its peak, is worth six Yahoos. That is because Yahoo meandered and grew bureaucratic under Mr Semel, lagging behind Google in search and Facebook in social networking.

Mr Yang and Susan Decker, Yahoo's president, therefore face a host of management challenges.

Their biggest problem is Yahoo's comparative weakness in search, which led Microsoft first to bid for the entire company and then to suggest taking over its search division alone. In response, Yahoo struck a deal with Google that allows it instead to keep working on its search arm.

Then there is Yahoo's complex and disorganised technology. Many Yahoo services run on incompatible software, which is highly inefficient. The technology confusion is mirrored in Yahoo's decentralised management structure, which has discouraged its business units from co-operating.

It also has to remain ahead of rivals in its biggest area of strength: display advertising. Some 87 per cent of its revenues come from advertising, much of it from putting ads on its own sites and those of "affiliates" such as WebMD, Ebay and 600 newspaper sites. Its revenues from affiliates fell last year because so many sites now compete for advertising.

Mr Yang and Ms Decker have put forward plausible plans to address all of these issues. They have already restructured management and want to keep expanding traffic on Yahoo sites, unify its technology and place more ads across the internet.

The difficulty comes back to trust. Mr Yang has a point that Mr Ballmer acted erratically after making his bid for Yahoo, which he finally withdrew in May. It is also fair to say Mr Icahn's slate is a bit crazy: nobody thinks oldsters such as Frank Biondi, a former Viacom executive, are a perfect fit to run Yahoo.

But then, Mr Yang's laid-back obstinacy can drive people, including some of his largest shareholders, mad. Like many young entrepreneurs from Silicon Valley, he appears to have an imperturbable belief in his abilities and the irrelevance of others' views.

In fact, there are good reasons for shareholders to doubt whether he can do what he promises.

Mr Yang is not a pioneer of technology, like Sergey Brin and Larry Page at Google. Yahoo was an early exploiter of the internet but its skills were in media not technology. Indeed, one of his Chief Yahoo roles was to guide technology, so he is partly responsible for the confusion.

Nor does he have a record of managing such a big and complex company: Tim Koogle was chief executive of Yahoo from 1995 to 2001, when Mr Semel took over. Mr Yang, who by all accounts is pleasant and unassuming in private, has always left management blocking and tackling to others, preferring to be a cultural and technological guardian.

I agree with Mr Yang that Microsoft ought not to be allowed to grab hold of Yahoo's search assets, leaving the rest of the company even more inchoate. If Yahoo is to be sold, let it be sold whole to any company that will take on the risk.

But simply giving Mr Yang yet more time to work on Yahoo does not strike me as an appealing outcome for shareholders. He has, after all, had 14 years on the job so far. That should have been time enough.

john.gapper@ft.com