One example of a failed prediction concerning self-replicating nanorobots is described at http://www.wisegeek.com

Early theories in The Engines Of Creation (1986), by "the father of nanotechnology," Eric Drexler, envisioned nanorobots as self-replicating. This idea is now obsolete but at the time the author offered a worst-case scenario as a cautionary note. Runaway microscopic nanobugs exponentially disassembling matter at the cellular level in order to make more copies of themselves - a situation that could rapidly wipe out all life on Earth by changing it into "gray goo." for more info go to http://www.wisegeek.com/what-are-nanorobots.htm
Written by R. Kayne copyright © 2003 - 2008 conjecture corporation

There are also success stories about nanotechnology including the nano-tubes used to kill cancerous tumors in rabbits at Rice University in Houston, Texas. It is hoped the new procedure can be used on humans in the next few years. (This is a good candidate for a future prediction).