I’ve written before about the issue of buried or implied technology in language.
But there’s another technology-related question that writers–especially writers of created-world fantasy– need to be aware of: What is the general tech level of your story?
A lot of created-world fantasy takes place in a pre-industrial setting. (Steampunk is perhaps the most obvious exception, but only if you consider steampunk to be a species of fantasy rather than a species of science fiction — a question upon which opinion is divided.) “Pre-industrial”, though, covers a lot of ground. Do you mean pre-gunpowder? Pre-clockwork? Pre-mass production and interchangeable parts? Does your society have steam engines or water wheels? Spinning wheels or drop spindles? Is your hero’s sword steel or bronze? Is his armor plate or chain or boiled leather? Does he pay the swordsmith in barter or with coin? Does his banker know about letters of credit and double-entry book-keeping? Has banking even been invented yet?
You need to think about all of these things if you’re not going to have your story taking place in an ersatz-medieval RennFaire fantasyland — and you need to make certain that your tech levels match across the board.
(Yes. This means that you have to do research if you’re going to write fantasy. Books like The Timelines of History and television programs like the old BBC Connections series are a good place to start.)
Dr. Doyle's Blog 
Not to mention, Connections is worth watching all on its own.
I keep running into interesting bits of technology in my early 19th century setting that surprise me — like the fact that when Chicheley Hall was constructed in the early 1700s, someone built a tower over a spring with a mechanism that would bring water to the upper floors of the house. Highly unusual for the time — and worth mentioning! It ran for 150 years, and it wasn’t the mechanism that broke, either — the tower fell in. I guess someone didn’t re-point the brick. 😦
I read Historical Fiction to explore a realistic period and Fantasy for a speculative plot, so I am quite forgiving of a fantasy world where some things are anachronistic.
However, I do get annoyed if the development level is unsupported so do agree that authors should research enough to know what precursors need to be there for a particular thing, so they can either make sure they are not obviously missing or add a different explanation.
I’m more likely to be annoyed in fantasy with environmental implausibilities – the FOOD has to grow SOMEWHERE, and rivers & oceans should make sense.
I must have been spared the food without production issue – or managed to blank it from my mind.
Farming is an area I tend to cut authors some slack. I might think it is unlikely a mountain tribe will subsist on corn and beef, but it will not spoil my enjoyment.