I have my family tree on Ancestry.co.uk as well as keeping it on my home computer using Family Tree Maker. The trees on Ancestry are arranged so that I have 4 trees, one for each grandparent and I have opted to keep the trees accessible to guests only. That means that if anyone does a search for one of the names on my tree they will be informed they need to email me via Ancestry for further information. I like doing it this way as it means I get contact with fellow researchers rather than them just going in and grabbing my research and wandering off into the sunset!
I have made several very useful contacts this way and we have exchanged information to everyone’s benefit. I allow these people access to my trees and they can then take whatever research is missing from their own trees. I must say the odd time I have got an email along the lines of “I want all your research” without any indication of what their connection is with my families tend to get deleted without replying, so Mr. B from New York that is why you haven’t heard from me!
Just lately I have had a couple of emails which asked for information and the connection between their family trees and mine is that one of their ancestors siblings married one of my ancestors siblings so there was no blood connection. With the advent of so much information available online, particularly the GRO indexes and census, it has become relatively easy to research family members back in time, forward and sideways. We can now gather up siblings and cousins of all degrees removed and place them on our family histories, but when does adding a person and their extended family to your family tree become irrelevant?
In my opinion the point when you should stop adding in names is when that person isn’t a blood relation to you. On Family Tree Maker the programme has a facility to calculate the relationship of an individual to the “Home Person” which in most cases will be you. I am sure other genealogy programmes have similar facilities and the use of this will stop you adding hundreds if not thousands of people to your family tree that bear no relationship to yourself. The obvious exception is one name studies or parish reconstruction when everyone sharing the surname or living in the particular parish are of interest.
This is just my opinion and of course genealogy is done for the pleasure and enjoyment it give to us so if you want to go ahead and add the pedigree of your 5th cousin 10 time removed wife’s sister husband then who am I to stop you!