Science fiction is a field that's profoundly vulnerable to being dated, probably more so than any other genre except possibly historical pieces, and even then they'd only be dated in the event previously unknown and contradictory primary sources came to light. The future's never how anyone predicts it, but sometimes things can go particularly askew, and as a result a reader's willing suspension of disbelief gets to take a body blow.
Oftentimes, it's because the author simply didn't see something coming, and the something in question reinvented society. This is most obvious in stories written before the 1970s, with advanced and miniaturized computers being almost entirely absent. Robert A. Heinlein's 1950s juveniles had astrogators plotting their courses with slide rules instead of calculators. Computation in much of sf tended to follow the UNIVAC model, being based around large, complicated systems which demanded a great deal of resources and attention, and yet still don't seem much better than a 2009 laptop.
Nevertheless, obsolescence isn't solely confined to technology, or the lack thereof. Personally, I'm a forgiving enough reader that, say, the absence of ubiquitous smartphones and the presence of a lunar colony in the "present day" is a sticking point - frankly, I'd prefer to live in that world. A lot of obsolescence is in the words themselves.
Arguments have been put forward that advancements in printing and literacy have reduced the speed of language shift. Four hundred years after Shakespeare, his writings remain fairly easy to read, perhaps with some squinting at word choices that seem odd today; in what was history to Shakespeare, Old English and Middle English resembled Scandinavian languages more than they did the language I'm writing in. That may be so, but if the language isn't changing greatly in detail, it rapidly fluctuates in specifics. When was the last time you heard someone describe something as "copacetic," for example, or use the phrase "23 skidoo?"
It's not just slang, though. On Friday I reviewed Tom Ligon's "Funnel Hawk," written in 1990, and there were occasional word choices in it that would have been innocuous then, but strike me as odd now. At one point in the story, the heroine is playing a flight simulator game that would make perfect sense as a modern MMO. It's the terminology that gets me - she "calls up" a simulation of the SR-71 Blackbird, when today we would say "loaded," and a modified joystick is described as using "the MicroSoft controls." From what I understand, the only other name Microsoft ever had for itself was "Micro-Soft." Certainly by 1990, the Microsoft name as we know it had been in use for a while.
These aren't major things, nor did they decrease my enjoyment of the story - they're just speed bumps. But, as speed bumps, they rattle me and for a second jolt me out of the story's flow. I'm not saying this is the author's fault - language changes, it's a simple fact of life. Look what the last hundred years have done to the meaning of the word "gay."
Personally, what I've taken out of it is a commitment to use a conservative narrating style. Simple, clear words tend to stay in favor. If I use an odd word, or if I use a few, generally I'll do it for flavor with a specific character. That, at least, might put it to my advantage.
Nevertheless, it's an aspect of the genre that can't really ever be overcome. There's no telling how words will shift meaning and which will date a story just as surely as one that features our Intrepid Space Hero and the Rogue Princess storming the Computerized Catacombs of the Emperor of Mars.
That might be kinda neat in any event, though.