The automobile evolved slowly from steam-powered vehicles - and trains could be seen as precursors as well.
Television could have been foreseen once radio was invented.
And I think steel has been known in various forms for a long time - but it was kept a state secret for most of its history.
No body saw Page rank's impact, but if you think it is obvious that reputation plays a part in relevance, then again page rank is just an obvious thing that built up over time.
The iPhone/Pod/Pad/XXX - if you say "simplicity" is the obvious killer in any product then they well it should have been obvious...
and the list goes on...
I think in hindsight a lot of what made the strategic innovations seem so obvious was well hindsight. It reminds me how MBAs are so great at explaining what has happened but are terrible at providing a plan with 0 uncertainty!