If you search for [-a], or [-b] and similar, you'll get (in my tests) 2 results, which can be expanded to 10... but they're all from YouTube. Does anyone know what's happening here?

http://www.google.com/search?q=-a

http://blogoscoped.com/files/result-for-excluding-letters-in-google.png

And these ones as well.
http://google.com/search?q=*&hl=en&filter=0
http://www.google.com/search?q=-the+-de

Probably don't want us to know how many pages/files are in Google's index.