Neighbors and Fences
When I was in high school my English teacher explained to us that Robert Frost's poem with the famous line "good fences make good neighbors" was intended to be an argument against having fences between neighbors.  I have to say regardless of the intent of the line I actually believe that boundaries should exist.  Perhaps it is because we live in a City with limited outdoor space; I like my privacy and I like knowing where I can and cannot plant and improve my own space.  Plus we had an issue with the placement of a fence and a neighbor who was trying to "empire build" by stealing land from each of us on both sides.  The other adjacent neighbor bought from someone who smartly had an easement drawn up and filed in the Registry, the previous owner of our home didn't care enough to worry about it.  In fact, I don't think they ever used this yard for anything recreational (thus explaining the multitude of yew buses and no pretty landscaping).

After several heated interactions with the land-stealing neighbor, we had our plot professionally surveyed and took back what was ours by title.  We did this in the event we decided to sell our house and the question of boundaries were to come up. (I didn't think we could legitimately sell our plot if the neighbor was preventing any new owner from access to it).  Plus, I was disappointed that we  had helped our neighbors on many occasions with snow removal, tree planting, and other odd jobs (they are older) and the attitude from them in regards to their installation of a new fence on our land, was  "tough luck for you".  Didn't seem fair somehow.  So not only did we get the land back, but we got over the feeling that we were obligated to help people whose values seemed skewed.

My moral of the story is be a good neighbor.  If you decide you wish to plant a row of privacy trees or install a fence, be kind and make sure it's on your property.