Worth a read: Pitfalls of Prophecy:
Why Science Fiction So Often Fails to Predict the Future , http://www.locusmag.com/2009/Westfahl_Predictions.html.
Why do they think that the fact that they write science fiction makes it worth listening to their predictions anyways? Well, besides the genre inferiority complex, which requires its hacks to pretend they're prophets, so they can feel important.