Everything posted on Gransnet is visible to absolutely everybody on Gransnet. Someone - anyone, in any country, with any kind of interest, medical, sociological, psychological, an individual who is estranged from their fanily or even someone who just has a casual interest - could collect the information and study it to provide an insight into the minds and motives of all the people involved.
There is ethical research, whether with the consent of the subjects or by gathering publicly available information for an informal assessment of attitudes and reactions, and on the other hand there is taking advantage of those same details provided freely by people on a public forum like the posters on here. If someone wanted to, and they took the trouble, they could probably identify those who had given a lot of detail about their relations and use the information against them somehow! I don't think ethics would be bothering anyone who had that aim in mind!