The suspension of disbelief is essential in the enjoyment of most fiction. You must be able to suspend your belief that the actor who played "Vinnie" in Welcome Back, Kotter could play a gigantic alien with dreadlocks. (Okay, poor example, no one could do that!)
You might be able to suspend your disbelief in magic and wizards and hobbits, but if Frodo finds a Ford Explorer parked in front of his house in the Shire, it could shatter the illusion and the compact made between the reader or the movie goer and the story teller.
A friend of mine, who once worked for the phone company, and I were both reading a sci-fi novel about some guy who invented or discovered a device (I forget which) which through some previously undiscovered high frequency sound, would give him hypnotic-like mind control over other individuals. My friend was okay with the book, until the character used the phone to remotely use his device a couple of times. At that point, he stopped reading the book. His knowledge of the exact frequencies that telephones were capable of transmitting, made it impossible for him to further suspend his disbelief.
Occasionally, I am jarred while reading of some "hard boiled" detective skulking down a darkened alley and clicking the "safety" off his revolver. Knowing there are no external "safeties" on revolvers, you start wondering what else they might have gotten wrong, too? And if I had a dime for every time I watched someone on TV or in the movies rack the slide of the shotgun they were carrying a second time, without ejecting a shell, then I could buy that new photoshop software I've been wanting to get!
Something similar happened this week, while I was watching the venerable "CSI":
One of the forensic lab guys was discussing the amount of corrosion on a weapon found at a crime scene. "It's a Ruger Mark III," he said. Then proceeded to expound on how it could have been there for "thirty years". Now I happened to have bought a Ruger Mark I about thirty years ago. I currently own a Mark II and know that Ruger didn't start production of the Mark III until about six or seven years ago.
At that point, I kind of lost the thread of the story, as I was asking myself: Who writes this stuff? Have they ever heard of "Google" ?? What else did they get wrong???
(As an aside, if you ever decide you need a small caliber gun that's fun to shoot that you don't plan on leaving at a crime scene, the Ruger .22 Mark series fills the bill! I used to line up soda cans, and after properly ventilating them, took them in to be recycled! )