I had a run in with a relatively new neighbour over this issue. They are chosing to use their front garden as a driveway (which is fair enough), but if people parked in front of their house (when car was not in the drive/garden), they would leave notes on the car window, or in my case, come out and confront me and ask me to move. Out of courtesy, I wouldn't park there generally, but i would've had to park in a different road and when I could see a perfectly good space two houses down from mine, I didn't see why I should. It all got a bit silly and over emotional on my part, if I'm honest, but I'm pleased I spoke up as i've not seen any notes on cars since. They had applied to have a dropped kerb, but the council declined due to it being a major bus route (or something).