Is Hong Kong Safe? in that in Hung Hom a building fell down
Hong Kong is semi safe, what the hell do I mean semi safe? , the below youtube video shows the damage in Hung Hom on the 29/01/2009 when a 5 story building collapsed. 5 people were killed and 5 severely injured. Oddly enough I stopped for some cup noodles at the 7-11 just to one side of the building.
Again this is related to water in that the older the building the less safe it is, concrete can last forever, however that isn't the issue. The issue is illegal renovations whereby interior load bearing walls are taken out to carve into smaller flats. Rents are high in Hong Kong $300 (US) is typical for a very small flat, greedy landlords will carve flats up into smaller units so that they can charge more for sq metre than before.
In newer districts say Olympic this is completely illegal and enforced so it is completely safe, however in older districts such as Hung Hom, Mong Kok or Kwun Tong (a nice picture is here). It is older and therefore there is a temptation to cut the flats into smaller chunks.
Although the Hung Hom building did not fall down instantly, the builders were seen and heard running away from the building 10 minutes before it collapsed and visible cracks appeared.
What is scarier is the Mong Kok acid attacker and general decay where things literally fall off buildings. My only advise is to ignore it, the odds of being killed in such an event is tiny, and Hong Kong has a world class health system. Other than perhaps Lantau and the outer lying Islands you are no more than 4 miles from a hospital.