I asked after we had become friends with them, had them over for dinner.... I suppose we would have put up more trees/bushes between our yards if it did bother them.

After a lot of use, the lines do eventually start to sag, so periodically we need to tighten them. After fixing many, many splayed areas, DP invested in some new lines last year and redid much of it. Kind of hard to explain the removable in-ground pole that they attach to, but if the lines are really tight, you can put the pole on the ground, pull the lines out (they all attach into a contraption that has a hook that hooks into the pole), attach to the pole hook and then lift the pole up and put in the ground. We live in a very wooded, natural looking area so I am glad that we do not have to have the lines up all the time.