Reading the question Why isn't Buffy a star athlete?, a further question came to mind....
Why does Buffy have to keep everything she is doing a secret?
Surely if the world knew about Vampires.... There could be a global effort to completely the wipe them out. Good things follow.
Sure, in later series the government "Initiative" appears which shows that things aren't quite so secret as she had thought and the US government being the US government they look to control the supernatural with great results*.
Nonetheless, is it ever explained in the early series why everything has to be kept a secret? Is it purely out of fear that nobody would believe and she would be locked up in a psych ward? Or is there a more believable reason?