I have been to the canyon in Matroosberg Private Nature Reserve where these accidents took place, and remember the one incident from when it was reported in the press years ago. It is truly tragic that lives have been lost, however, I simply do not see how the blame can be shifted to the owners of the Reserve.
Here is the link to the article online: http://www.iol.co.za/news/crime-courts/family-to-sue-after-mountain-death-plunge-1.1500992#.UW0oIbVkN8F
I will be very interested in the outcome of this case. It is my opinion that there is an inherent risk involved in participating in any outdoor activity. As a mountain / ocean / river user, it is your responsibility to know the environment you are entering.
By definition, being on a mountain involves heights of some kind. You need to be aware of this at all times. In addition, you need to take current conditions and prevalent conditions into consideration, such as footing which may be compromised by moisture, snow and ice.
I do not believe that the responsibility to do so shifts depending on whose property you are on.
I would go as far as to say that the extremely high cliff, providing a breathtaking view of the canyon, and the snow, are exactly the features of the area that bring people to the spot in the first place, and as such it is not as though you can be claim to be unaware of either.
I think that one of the problems in this specific spot is that people are able to reach the immediate area by 4×4, meaning that people with little or no mountain experience could suddenly find themselves in a relatively dangerous area. It is for this same reason I am opposed to the protection on the India—Venster Route on Table Mountain as it allows less experienced mountain users access to an even more dangerous area of the mountain — see more here. However, once again, as a 4×4 user you should be well acquainted with the outdoors, and as the driver, you are certainly responsible for the safety of your passengers.
In the photos below you can see there is a warning sign (I have no idea when it was put in place).
I trust that common sense will prevail and that the owners of Matroosberg Private Nature Reserve will be successful in defending the case. If not I fear our wild spaces will become ugly, sanitised spaces filled with warning signs, guard rails and protection devices better suited to construction sites.
Articles regarding accidents at Matroosberg: