Wow, that's HUGE! It's a shame that they built it so close to the fence, but they have that right I guess. The only thing you can do to protect yourself from things like that is to either build right in the center of your property, or to do it to them first. ;o) Really though, I know of people who have built something right on the fence line to discourage any prospective buyers of adjoining property from building a house right next to them. Nothing like a chicken house or hog house to make you wanna back off.
Precious doesn't hesitate to jump in.