The famously reclusive astronaut Niel Armstrong has written a detailed reply to a column by NPR's Robert Krulwich regarding why the Apollo 11 mission seemed so limited. It's my understanding there were very firm distance limits set by NASA on all the moon landings to ensure the astronauts could rescue themselves if something went wrong with the space suits. Discovery dedicated a documentary to what would happen if, say, the rover fell down an unseen ravine when it was far from the LEM. The conclusions were, "it won't be pretty."