I have no folder named "Bitcoin" in Application support,
I'm an idiot but I am a Mac user and being new to
BTC I ran into this problem as well after buying a new MBP this past weekend.
First, are you looking in your user folder and not the system Library folder? <Your User Account/Login>/Library/Application Support/Bitcoin/
Which OS version are you using because I learned that by default Lion and Mountain Lion hide the user Library folder.
If you're using 10.7 or up,
check this out and then try to find your Bitcoin directory.
Hope this helps if it is in fact the snag you're facing.
Cheers!