Lucy Kellaway: Interview- Jim Buckmaster doesn't believe in maximising profits. He doesn't believe in management. He doesn't believe in brands. He doesn't believe in discussing money and he doesn't believe in smiling.

So much I had found out before meeting the chief executive of Craigslist, the internet classified advertisement company that claims to have twice as many users as Amazon - yet employs just 25 people out of a Victorian house in San Francisco.

Ahead of our meeting I gave myself two modest challenges: to make Buckmaster talk financial and to make him smile. After all, he has enough to smile about. In 1999, he was an unemployed web programmer who posted his resume on Craigslist, where it was spotted by the website's founder, Craig Newmark, who offered him a job. A year later he was made chief executive and now he is in the most delicious of positions. Hugely successful, he could also be hugely rich if he wanted to cash in his stake. Only he chooses not to. The high moral ground suits him better.

Buckmaster ambles over to where I'm waiting at his chintzy Chelsea hotel. He is ridiculously tall (6ft 8in), is wearing flip flops, has dark hair with streaks of grey and is unshaven. He is decidedly attractive, so I'm disappointed that he directs his greeting and all subsequent remarks at the potted orchid over my left shoulder. He does not smile and his handshake is limp.

I tell him I usually conduct interviews like this one with the chief executives of big companies such as Nissan - whereas Craigslist is worth . . . how much? This attempt to extract some numbers falls flat. "Er. We don't give out financial metrics," he says in a halting sort of way. "But I guess we have 25 million users each month. I don't know how many customers Nissan has." Users flock to the site to sell houses, second-hand sofas and their bodies - prostitution taking its place as a service for sale alongside ear candling and trumpet lessons.

Most advertisers don't pay, though estate agents and firms placing job adverts pay between $10 (€7.22) and $75. How much is raised he won't say.

The runaway success of the website is odd. The name Craigslist is awful and the page-design - a long list of categories in tiny, cheap-looking type - is non-existent. "We try to stick with what the user finds useful." So the website is clear and fast. Users don't like pop-up ads or big logos, so there aren't any. The company has one principle - to please users - and follows this doggedly.

But what about motivation? If you shun profitability, isn't it hard to get motivated? He disagrees. "I get e-mails from people who have assembled their entire lives off of Craigslist. They've gotten their current job, spouse, the place they live, their friends and their dog off of this site. It's a direct sort of philanthropy. We are helping people through our service."

There are at least two ways that Craigslist is not helping. Earlier this summer the mayor of Atlanta was the latest to complain about the hookers who use it to tout for business. "The US is very fixated on matters of sexuality," Buckmaster sighs. "It's mildly tiresome at times."

He is equally unmoved by claims the success of Craigslist puts newspapers out of business and costs jobs. "Newspapers are still very profitable," he insists.

But if philanthropy is the aim, why not raise more revenue and give more away? "We don't have any genius for giving money away. It's difficult and time consuming. We give away 1 per cent of our revenues, and that is hard." So is that about $2 million? I ask, hopefully, but no dice. "That might lead to unfortunate back-of-an-envelope calculations," he says.

I show him a cutting saying the firm is worth more than a billion dollars. "I don't really know if that's true or not," he says in a faraway voice. In any case, he says, it's hypothetical as it is not for sale. Isn't he sometimes tempted? "No, I'm not. We run the business the way we want to run it. We have lifestyles we are satisfied with. We find this very enjoyable and fulfilling."

These days he is increasingly in competition with the toughest internet companies, which are moving into classified ads. One competitor is eBay (which bought 25 per cent of Craigslist from a former employee in 2004).

Buckmaster doesn't seem too interested in the threat. "From the users' perspective it can't be bad if we are ever displaced by someone doing a better job," he says, though clearly he doesn't see that happening soon.

So what does he worry about? He pauses. "I worry if I've made the right decision in keeping the company so small." More people would mean more brains to serve users - but large organisations are dysfunctional.

Small ones can be too, I say. He agrees: "Yeah. You just mustn't screw it up."

The interview is over and I have failed: no smile and no numbers. The photographer arrives and I suggest the picture is taken outside as the hotel is too frumpy. "Frumpy?" he exclaims, inexplicably amused. He smiles, broadly.

It seems the minute I stop trying, I succeed. Which is a little like Craigslist. While all those other internet companies strived so hard to make money and went bust, Craigslist wasn't trying at all, but hit the jackpot.