The bad news for companies trying to sell their goods online to young Chinese consumers – who are both the world’s most internet savvy and most spendthrift – is that they are increasingly dubious about the credibility of online advertising, according a recent McKinsey study of Chinese consumer attitudes.

The good news, says the report, is that there has been a “sizeable increase” in the percentage of consumers who trust product information they get on social media.

McKinsey says the popularity of social media – services like Sina Weibo, the Chinese Twitter – is growing at a “staggering” rate in China (including a tripling of the number of Chinese that had used Weibo in the first six months of 2011, to 195m).

Chinese social media users have not yet fully got into the swing of using such services to tell each other what to buy.

Only 20 per cent of the internet population in China use social media to share information about products with other consumers, compared with 37 per cent in the US, says McKinsey. But that number will doubtless grow, given the rise in willingness of social media users to believe what they hear from other people.

That means companies need to learn how to project their brand image, not just on television, in print and online, as in the old days, but increasingly on social media, according to Mark de Swaan Arons of Effective Brands, the global marketing consultancy.

Durex, the condom brand, is a model for how to do that in China, says Darius Karbassioun of BBH, the advertising agency, in Shanghai. At last count, Durex had 241,023 followers on Weibo, the leading Chinese microblog.

Why on earth read about condoms on Weibo? It seems Durex sees its mission as educational: the condom maker’s Weibo followers can enjoy, among other things, lessons in the art of kissing: “Start from kissing his/her hair, face and then gently move to the mouth”. With that kind of thing available on Weibo, who needs blue movies?