Oh, if that's what you're talking about, then it just becomes dated. That has little to do with "fun" unless it's (IMHO) really, REALLY stupid.
Example: Our bookclub recently read the reprinted omnibus edition of the Sector General series by James White (the first three are reprinted in "Beginning Operations"). Now, in one of the stories, White describes all the scientific information for a Brontosaurus - current as of 1962 or so. Ok. He was accurate for the science *of the time*, and completely inaccurate for 2012, but that didn't make the story any less fun.
(small) Counterexample - social change that has outstripped the writing - the most harmless example I can think of are the ubiquitous (female) secretaries for police detectives in the future of "Do Androids Dream of the Electric Sheep?" Ok, that's not a science thing, and it's not that much of a thing in the story, but it's an example of how that sort of dating can make things Not Fun.