How do you hide your profile picture on Facebook?

Account (top right corner),

Privacy Settings,

Customize settings (bottom of Sharing on Facebook" list in blue),

"Edit privacy settings for existing albums and photos" (bottom of "Things I share" list in blue),

Click on box under profile picture album,

Click Customize,

Change to "Only Me"

This only makes people unable to enlarge your current photo or see your other profile pictures, but the small version of your current profile picture is always visible. The only way that I know of to hide it completely is to delete it.