I can hide the toolbar in Finder by pressing option+command+T. However it only saves this to the .DS_store file in the folder I do press the command. I'd like to have the toolbar hidden as default, as I only use shortcuts anyway and I like the extra viewing space it gives.
I don't know any way to hide the toolbar by default, but you could drag all items out of it after selecting Customize Toolbar from the context menu.
Or run something like this in AppleScript Editor: