There are now estimated to be more than 200 million personal web diaries or blogs online. Their content is now shaping opinion, making and braking brands.
Many people believe comments about - say - a hotel in a blog far more readily than they believe an official corporate site.
Question: which do you trust more? Online adverts on a search engine, or a community website? My own informal polls of senior executives around the world suggests that unnoficial community sites win almost every time.
It spells the death of traditional advertising and brand management.
If the blogs come up high in the search engines and contain a lot of negative comment about your product, no amount of web advertising is going to help you.
That's why some companies are now employing people to post positive comments about their products and services on bulletin boards, blogs and other community sites, disguising the fact that their agenda is a paid promotion campaign.
It is building up to be a serious issue - and one hafrdly understood by most large corporation leaders.
A prime example is the leisure, travel and hotel industry - just type in the name of a large hotel into Google and see how far down you need to look before you hit a site like www.traveladvisor.com.