7. The Secret Of Kamino
The Moment: Obi Wan takes a piece of evidence (a dart) to Dex, an alien bartender who not only recognises it, but tells him all about a planet of cloners called Kamino where it was made. When following up on this information Obi Wan discovers that the planet has been erased from the Jedi Archives in an attempt to conceal its very existence.
Why it's Dumb: Erasing mapping data on a house, or a even a small village could feasibly prevent anyone knowing about it if they weren't looking. But an entire planet? Seems far-fetched indeed, especially considering random aliens in seedy bars can identify tiny darts that were made there. For the plot to make sense here we must assume that the Jedi Archives are the only planetary maps in the known universe; not impossible, but extremely unlikely.