Hi,
I've had some unpleasant dealings with a few people on GR but the pleasant ones far outweigh the unpleasant. Discovered quite a number of cousins of varying degrees of kinship including two second cousins I knew nothing of, one a year older than myself, was born and raised and still lives on the opposite side of my hometown, unbelievable.
Due to the unpleasant people I now have set myself some rules to observe before giving access to my tree or passing on additional info concerning the tree.
1) Need to be assured that the person is definitely related to someone in my tree.
2) They are researchers as opposed to collectors.
3) I only put the year of an event on my GR tree not the full date, there are one or two exceptions where I have added full dates such as where I need to repudiate false claims in another tree concerning my lines.
4) I do not show the earliest known ancestor of each line on my GR tree, only 100% genuine ancestor related researchers get that info.
I am very happy to share my findings with genuine people.
There is one young lady on GR who has constructed a tree on GR with info gleaned from GR, Ancestry.com and Family Search. Consequently she has one of my Essex ancestors Joseph Willis, married with a family in Devon under the surname Wills, in Essex she has him married correctly with a family under the surname Willis, then married again to another lady in Essex with a family, again named Willis. Stupidly she shows the children of the Devon marriage overlapping with the children of the first Essex marriage and then the children of the two Essex marriages overlapping. This young lady is or was at the time a Uni student, I just hope her Uni subjects were better researched. Coincidentally I checked a couple of weeks ago and now some two years later the error remains, at the time she first made contact I did diplomatically point out the flaws in her tree. All I can say is that if my ancestor Joseph Willis could have pulled off a feat like that he's a far better man than I.

Regards.