Good Fences Make Good Neighbors?

Today my next door neighbor and I had a little chat about the fence he is going to build along our property line. Three years ago I would have said, "That's cool," and gone on my merry way. How law school can change you. For a moment I was panic stricken. I should really make him hire a surveyor. What were those rules for adverse possession we learned first year? Make sure you don't concede anything. If this blows up in 10 years will I be able to reconstruct this discussion? Shit, I should just cut my losses and sell the house now. It doesn't help that the very first "real" case I worked on was a property line dispute concerning a purported partition fence. And these are neighbors I really like. Sheesh. If this is what my world is going to be like, I don't like it one bit.