I for one think we did indeed land on the moon. It's just too big a conspiracy to keep a secret. With so many people involved in building an actual spacecraft, doing research, training the astronauts etc. not to mention outside observers [press, other countrys, astronomers etc] there's no way in hell NASA or the US government could keep this a secret..
As for why we didn't go back.. Well, I've never been to the moon so I wouldn't know about any bases on the dark side..
I think we didn't go back because we accomplished our goals on the moon: We went, we explored, we left. End of story. Sure, NASA could go back, but the cost would be astronomical, and it'd mean diverting resources and manpower from other more deserving projects: the ISS, mars exploration, etc.