As the Electronic Frontier Foundation's Kurt Opsahl notes, Facebook introduced this concept using the innocuous topic of "cooking." Who wouldn't want to be known as a fan of cooking? Unfortunately, the same rules apply to more controversial pages you might also like:
"Previously, you could list "cooking" as an activity you liked on your profile, but your name would not be added to any formal "Cooking" page. (Under the old system, you could become a "fan" of cooking if you wanted). But now, the new Cooking page will publicly display all of the millions of people who list cooking as an activity.
"Cooking is not very controversial or privacy-sensitive, and thus makes for a good example from Facebook's perspective. Who would want to conceal their interest in cooking? Of course, the new program will also create public lists for controversial issues, such as an interest in abortion rights, gay marriage, marijuana, tea parties and so on."
PC WORLD: Facebook Gets a Little Too Personal
Go to Account > Privacy Settings > Applications and Websites > Instant Personalization and uncheck "Allow".
When you uncheck the box the following pop-up appears:
FWIW if your friends don't do this they will be sharing information about you.