There are several types of buildings which present special hazards in the case of an earthquake.
Unreinforced masonry buildings tend to be older construction, residential type structures. Areas with frequent seismic activity, such as California, have long standing regulations prohibiting the construction of such structures. However, there are still thousands of such buildings in earthquake prone regions. Even more scary is the prevalence of UMBs in regions with the potential for a large earthquake, but less common earthquake activity. Because so many of these structures are private homes, municipal or state efforts to retrofit these structures are difficult.
Non-ductile concrete structures are also particularly hazardous, and can be difficult to identify from cursory inspection. In California, many concrete frame buildings built prior to the mid 70's are of this type.
Determining liability in the case of an injury caused by a design inadequacy can be complicated, but a commercial business which is aware of such issues is placing itself in a very dangerous position if they choose to avoid taking steps to earthquake retrofit. Of course, the cost and effectiveness of the available modifications should be balanced against the risks, but a jury is not likely to be sympathetic if known issues result in the injury or death of a third party.