As the internet can offer glimpses of a long-obscured past, it may be opening a window on a potentially darker future. Take a recent example from YouTube. A few months ago, footage started appearing purporting to show the naval clash in 1988 between China and Vietnam in the disputed Spratly Islands in the South China Sea. At the climax, a group of sailors standing shipwrecked on a reef are cut down with heavy fire.
More than 70 Vietnamese sailors were left dead or missing after the brief battle that saw China take control of six islands. Largely forgotten, it remains, however, the last significant naval battle anywhere in East Asia.
The most striking aspect of the footage is not the battle - given the decrepit state of both navies 21 years ago, it is hardly The Hunt for Red October - but the online hatred it has inspired.
The comments from both Chinese and Vietnamese nationalists are some of the most caustic you will find on the Net, laced with racial expletives and sexually violent taunts. It is a stark reminder of the perils facing both Communist Party-run governments as tensions in the South China Sea rise once again.
Both are pressing their claims to the South China Sea and both, at times, have shown themselves entirely capable of manipulating nationalism for their own ends. Both, however, know that nationalism is a tricky tiger to ride.
There is nothing to suggest that either government was behind the posting of the footage. But it has apparently fuelled a cottage industry in hostile Sino-Vietnamese postings. Footage of the brief but exceptionally bloody border war between the former allies in 1979 - the most ironic conflict of the cold war - is a hot favourite. It is also accompanied by similarly toxic comments.
The world has changed a great deal since then. China and Vietnam formally normalised ties in 1991 and, while lingering suspicions and mistrust remain, progress is being made on many fronts. Trade, investment and tourism are gradually expanding, matched by a rise in official engagement. Disputes across the land border and in the Tonkin Gulf have already been solved through negotiation and just the thorny issue of the Paracel and Spratly archipelagos - both highly strategic and resource-rich - remains.
Once, both societies were closed and tightly controlled, and such dangerously provocative imagery now available online was largely kept locked in the files of the state media propagandists, and occasionally dusted off during moments of tension.
Now, the internet provides a free-for-all (China still bans YouTube, but it is easily accessed via proxy servers on the mainland). Both governments must respond to such openness with displays of real regional leadership and maturity.
Nationalistic sentiments have already shown the potential to drive a wedge in relations. In unprecedented scenes, Hanoi students converged on the Chinese embassy in December 2007 to protest against China's claims to the South China Sea. Beijing was not amused.
Hanoi officials were also left in no doubt that China was not willing to tolerate any similar protests during the appearance of the Olympic torch in Ho Chi Minh City last year.
Hanoi has for years made its own claims, in what it calls the 'Eastern Sea', a core part of its propaganda narrative. But, now, domestic and foreign-based dissidents are swift to criticise any perceived government weakness in the face of a rising China.
At the first international academic conference on the South China Sea, in Hanoi last week, rival scholars agreed on the need for both governments to lower temperatures surrounding the issue, noting that nationalistic sentiments had not been managed successfully by either side.
The internet, and YouTube with it, is now a fact of life. But whether the likes of Beijing and Hanoi can show the openness and flexibility required to help boost relations, despite outstanding disputes, is much less certain.
Greg Torode is the Post's Chief Asia Correspondent