Like most people on here I keep a tree on Genes and Ancestry, but I do not keep any detail on them, just names, year and place of birth. I have had made friends, some on the otehr side of the world, and obtained some useful information from contacts on both sites, with joint efforts in some areas helping clear up the grey areas BUT all the detail is kept on my own software on my home PC. I did initially start to keep some detail (nothing too personal, DOBs for deceased ancestors) but having had some issues with people taking details from my tree without asking (including details of living relatives) I decided the safest thing was to hide living relatives on both sites and only put the bare minimum of information for everyone else. One person who had about 300 names in their tree did actually ask if they could copy all the details of all my living relatives onto their tree even though their link was via a marriage 3 generations back, so not very close at all. I asked them not to copy details of living relatives and they weren't too happy and sent me a very sharp email saying that in that case I should remove any reference to their ancestor from my tree ( a member of my direct paternal line married their ancestor) - it was at that point I made the decision to change to change the way i post my info on the net. That person now has over two thousand names in their tree!
Anyway, at least now, through email contact I can determine how genuine someone is, and how close their link is, and ultimately how much or little information I share.
I like everyone else am amazed at people who name collect - I don't understand what it achieves. My aim is to learn about my ancestors lives, their history, which is why i only have some 700 names in my tree at the moment. I could have thousands if I simply wanted to list every single person who could possibly be related, but what is the point because then that's all they'd be - just names.