yesterday we had a fence installed. a nice, 4' high, three rail, split rail fence. the fence runs across two borders of our yard - the back of our yard, and the side between us and our messy and (somewhat) intrusive neighbors with the dog that relieves himself on our lawn.
not that the fence will help keep the dog out, but at least now I have something to pitch stuff over that isn't ours; a nice and clear distinction between my property and theirs.
many people point to Robert Frost when it comes to fences: "Good fences make good neighbors." Personally, I prefer the timeless logic of Woodie Guthrie: "This land is your land, this land is my land."