From what I'm noticing on the Internet, one of the things that no one ever really talks about in regards to being a scientist or professor is the torrent of completely unsolicited "theories" that pour in claiming to debunk relativity, solve a Millenium Prize problem, describe a perpetual motion machine, and every outlandish, bizarre, or just plain unworkable idea you could imagine. What I'm curious about is, what happens to these people? Now, to be sure, some of these people are just plain unhinged. But mental health problems wouldn't explain why some intelligent, competent scientists and engineers fall in with odd (or just outright delusional) ideas. Or, a bit more lightheartedly, where do mad scientists come from? And, moreover, what should aspiring scientists and engineers do to avoid becoming crackpots?