I first learned about the Missingno glitch from a family friend. When I got home, I taught my friends from school about it, and everyone started glitching. Unfortunately, it wasn't long before I regretted sharing my newfound knowledge.
For whatever reason, Missingno used to terrify me when I was younger. The hall-of-fame data corruption and sprite scrambling scared me, and I was convinced that if I traded with a friend whose game had become pretty screwed up due to glitches, his glitchiness would infect my game and destroy it as well. I tried using the Missingno glitch a few times, and liked multiplying my items, but I didn't want to catch any of the glitches. Also, the multiplied items made the game seem too easy. I was actually so bothered by the fact that I felt like I was cheating (while risking screwing up my game) that I restarted my file. That was my second completed Pokémon game (my first was well-protected on a Mega Memory Card), and I had a lot more fun with the first and the third than I did with the Missingno/glitch one.
Learning about Missingno inspired me to spend time researching glitches, so as to avoid accidently ruining my game with them. I recall spending numerous Friday afternoons in elementary school reading about glitches in RBY, and later, GSC (alone with all of the garbage that came along with them--Pikablu rumors, evolving Dragonite into Yoshi, and the like). Since then, I've actually begun to find glitches really interesting, and I've tried to learn more about what causes them and how they work. Now that I'm older, and I understand them better, they're not so scary. But my original reaction to them provides some insight into how we deal with the unknown, and how our interpretations of situations change as we gather more information.