Castle? Folly?

There are several bulletin boards out there that have castle-centric discussions, and a few that leave room for people to discuss the building of modern castles. There is always a debate (sometimes nasty) on what constitutes a real castle, and a folly.

Well, after learning a bit more, in my opinion: A real castle is one that was built prior to the 1600s and the primary use was defense and domestic living. The naming of modern built structures with the term castle isn't quite correct, as these structures are not purpose built for defense; they are simply very unique homes. That said, use of the term "castle" to describe them doesn't bother me in the least.

A "folly" is pretty much what most people will build nowadays, and that is a home that has some castle-like features. I guess if I were to build one, it would be a folly; a structure not made of pure stone, having a stone facade, and primarily being a residence. There are some folks out there putting together structures that blur the line between castle and folly, they are well constructed of pure stone (ashlar and/or rubble) and could possibly be used for defense. Therein lies the debate. As far as I'm concerned, the debate is academic; if it looks like a castle, it'll still be called a castle, regardless of the purist's ranting.

EDIT: After learning a bit more, my definition of a folly isn't right, a "folly" serves no real practical purpose other than fancy or artistic design. A home that is in the style of a castle is exactly that, a home that looks like a castle. The Germans have a word that describes those structures much better: "Schloss".