So here's a little story about the neighbor's across the street from my mother. The folks off to the right moved in less than a year ago. The tree you see in the picture was not trimmed at the time, and came way over onto their property, killed all the grass, blocked the view out of the driveway, poured sap on their cars, etc.

They went back and forth with the neighbors on the left to rectify the situation. Asking to trim the tree, maybe cut it down, offering to help pay for it, etc. The neighbors on the left being militantly environmental refused, then started spreading some very mean spirited rumors about the neighbors on the right.

Finally, after consulting with lawyers, the neighbors on the right found out that they were able to trim any branches that came over their property line. The City actually said they had to because it blocked the view of the sidewalk and was a safety hazard!

So there you go. You can check out some more pics here.