Firstly, You can come to know if some hacker has your password or someone else is using your account. You can get an get an sms or email notification whenever someone opens your account. Facebook has termed it as "extra security". This feature lets you know the location of opening, time, browser and the operating system of the user. If you find any unknown location you can terminate opening of your account at that location by clicking on "end activity" against that location.
Secondly, The thing that i experimented on facebook to check the above claim. I tried opening my friend's account (the friend gave me the password) and there was a test to check whether i am the same person or not. The test had photos of five different friends with tags in 4 to 5 photos and i had to identify the person tagged. This is repeated for 5 different friends and you can skip 2 out of 5 friends that means you have to correctly identify 3 of your friends correctly.
Thirdly, the improved privacy page with the recommended settings.
One more thing which is insignificant according to me i.e. you can control placing your name in things such as "xyz" likes "abc". This can be done by going to "Facebook Ads" tab in "My Account" page.