I still get a lot of that WHO BUILDS THAT PLANE crap at every field I have gone to. When it first started happening it would piss me off but then I figured that if someone couldn't tell it wasn't an ARF I did a good job. All the ARFs look pretty good these days so I now take it as a complement. It's also a fun thing to play with. Depending on my mood I often make up fake manufactures names and tell them that or come up with some BS story about where they can get one.
It no longer bothers me and with so few people building these days it's a pretty normal question.