No No! You Don't Want That!

You DO NOT want Facebook to use your picture to illustrate ads WITHOUT your consent! So, change your settings now:
Click on SETTINGS [next to the logout button] and select PRIVACY SETTINGS. Then click on the NEWS FEEDS AND WALL link. Click on the FACEBOOK ADS tab. Then, select the NO ONE option from the drop down menu and save your changes.

Here is a bit of visual help for those who got 'lost in explanations'...