In Hong Kong, the 'bus uncle' saga has stirred intense debate in internet chat rooms and on radio phone-in programmes about the phenomenon of rude passengers on public transport.

The saga began with dissemination of footage, shot using a mobile phone, of a middle-aged bus passenger bullying a young man who complained he was talking too noisily on his phone.

The footage shows Bus Uncle shouting down the young man. Soundbites from the harangue have become the talk of the town. 'I face pressure. You face pressure. Why did you provoke me?' was one comment. 'This is not solved. This is not solved,' was another.

Despite the marked differences in the three Chinese societies, the three episodes have highlighted the power and influence of a free, open and independent press - and of new media, in the case of the Bus Uncle saga - and of the free flow of information.

Critics and cynics may consider the case of Taiwan a counter-example of the failures of democracy - money politics, voting irregularities, corruptions, scandal. You name it. But the fact that alleged wrongdoing by a member of Taiwan's first family has been uncovered shows the power of the media and is a reminder that the power of the people, expressed in the voting booth, can restrain or punish abuses of power and maladministration.

Undoubtedly, the media on the mainland is still far from free and independent. If not for the involvement of Hong Kong journalists, and the fact the assault was taped and broadcast widely, the ugly scenes outside the Shenzhen hospital might have never come to light.

To mainland journalists, the stormy encounter was hardly uncommon. For social, cultural, economic and political reasons, the concept of the media as the fourth estate is absent north of the border.

The Shenzhen mayor decided to act so swiftly because of the damaging impact of the footage on the image of a city eager to open its door wider to the world, a city hoping to foster a closer economic partnership with Hong Kong.

Following the broadcast of the footage, radio phone-in programmes were flooded with calls from Hongkongers sharing similar experiences on the mainland.

Chief Executive Donald Tsang Yam-kuen calls a free press and the free flow of information one of the four pillars of Hong Kong's success.

The proliferation of new media and a 'clip culture', as manifested in the Bus Uncle saga, has added vibrancy to the media scene and public debate. The sharp increase in the speed and scope of information dissemination through a wide range of media poses a fresh challenge for media professionals.

One lesson to be learned from the recent controversy over alleged mass cheating by Form Five students using mobile phones in an English exam is that journalists have to exercise extra caution over the authenticity of information posted on the internet. An investigation by the examination authority of the claim that examinees went to the toilet and accessed a website to help with an answer cast strong doubt on the claim. That being said, there is no doubt the rapid advances in media technology have brought more good than harm by allowing more people to get involved in discussing issues that affect their well-being.

With a free press and free flow of information, views can be aired and debated vigorously. That can help build a consensus about controversial issues.

This is part and parcel of a pluralistic Hong Kong society. For that to remain the case, it is important the media shows independent thinking, good sense and professionalism in the exercise of its power.