I wondered this, too. I have mine completely empty so it's just an empty space, but even when I was testing and put "English" down as language (with the privacy setting set to "Public," of course), that didn't show up on my profile, but it showed where I was from and other information. Didn't know why it would show different information for different people, regardless of whether you had the privacy setting set to "Only Me" or not. I haven't tried in a while, so maybe it works now...
In any case, to hide your information, click on "About" and then click "Edit" on "Basic Information" and change your privacy setting on each section to "Only Me" or "Public" depending on what you want to be shown on your profile or not.
...Vin
