Build astronomical observatories on the Moon?

What can be the moon good for us? Of course it is beautiful. I also like to visit tidal pools by seashores during low tide. Serious scientists is thinking about doing serious science on the moon, and politicians might be considering how to justify Bush's space policy of a moon base. I enjoy the out-of-the-world debate whether we should use moon for a massive observatory on Physics Today. There are so many unthinkable issues that common people like me won't dream of on the moon. How do you think? Can you justify an observatory on the moon?