I don't see the point in searching for "unrealistic" details in SF. Do you really believe that it is possible to describe (and explain "scientifically") ALL aspects of common life and technology in a far future? "Orwell did not predict cell phones OMG He's so outdated!!!" - This way? I don't think that even pretending to the realistic description of everything is not very wise because it means obvious and predictable epic fail.

For me the difference between the truъ and would-be SF is the main purpose of the author. If the purpose if to predict\warn\admire about something new that comes out with a sci/tech (and connected social) progress - it is truъ. If the main purpose is to entertain/stylize/escape-the-reality/get-the-profit/whatever else - it is would-be SF. That is subjective of course (as everything) but I believe that the criterion is clear enough for the most.

Also I believe that the main purpose of SF is a social aspect rather than technical. Fiction literature is a humanitarian tool and solving technical problems with it does not look like a good idea. Can you name a single technical prediction of Jules Verne that does not come out as obvious fail? Submarines? Hey, sample submarines existed before Jules Verne. Jules Verne is about the spirit of the modern age, not about the particular technics or physical laws.