Phil Grant has written a letter to the Guardian on the subject of Jackie Ashley's latest column, on the influence of betting on the political process. This is topical because of the coverage of the Liberal Democrat leadership election, in which there have been frequent references to the changes in betting odds.

Ashley clearly disapproves of this influence, though it might be worth wondering why she disapproves of it. The obvious accusation is that, as a journalist, she feels that she (and her colleagues) should maintain their monopoly on political analysis, and that alternatives posed by betting, prediction markets and internet-based commentary are threats to that.

Of course, she does make some good points. Bets are made with less than perfect information and it would be very foolish to use the betting odds as your only source of information about future events. But any of the criticisms that can be made of the betting markets - that they distort perceptions, over-reflect marginal or arbitrary judgements, give false momentum to causes or candidates - can be applied just as well to journalism.

Ashley writes: "These judgments are not just a bit of fun; in leadership races, momentum is everything. The question of who wins may not be decided by such stories, but they help. And there is a small, tight, spinning circle of interlocking judgments being made that needs - in the interests of all of us - a bucket of cold water thrown in its general direction."

Could not the same comment be directed at the Westminster commentariat? The "small, tight, spinning circle" of journalists, spin doctors and PR men and women are surely just as much to blame?

Ashley's contention is that betting markets are not just reflecting people's views, but are influencing them. The argument is that people see the odds on, say, Chris Huhne to become next leader of the Liberal Democrats, and this makes them more likely to support him. But I think this is to mistake the cause and effect; Huhne's odds would not have shortened in such dramatic fashion unless a significant number of people were already willing to support him. It's true that commentators like Mike Smithson of politicalbetting.com may have the power to shape opinions, but surely no more so than any other political commentator.

The Wisdom of Crowds is a popular book by James Surowiecki. In it, he makes a strong case that the many are smarter than the few - that you get better and more accurate judgements by asking a large number of diverse people than you do by relying on a small elite of experts. Surowiecki gives numerous examples of situations where small, close-knit groups of experts are unable to formulate accurate views. This is because experts generally tend to think alike. For someone to be recognised as an expert, it is necessary that they think like other experts, and this leads to a gradual loss of connection to reality. Contrary views are not presented and expert opinion becomes unable to respond to things that don't fit with its world view. Liberal Democrats will be very familiar with this effect, given the notorious difficulty of the press in abandoning its two-party "left vs. right" mindset. In contrast, more open systems - democracy and markets, for example - do not suffer from this effect. For more information, see the Wikipedia article on the book.

If we accept the thesis that open, diverse systems produce more accurate judgements than closed, private cliques, might we come to the conclusion that betting markets can actually tell us more about the world than newspaper columnists? It's tempting, but ultimately such a conclusion can't be supported. Politics is so often a matter of opinion, in which no single opinion is necessarily the sole truth. Betting markets can tell us what people are thinking. They can sum up opinions into very simple variables - odds on particular outcomes. But they don't tell us why the punters think that, or what might change those opinions.

A sensible view would be to take account of multiple sources of information. Betting markets are useful, and so are journalists and, of course, so are blogs. But equally, so are the opinions of your friends, colleagues and social circle. If the Wisdom of Crowds tells us anything, it's that the opinions of ordinary people are often just as important as the opinions of self-appointed experts.