Facebook

Facebook has unveiled a redesign of its News Feed, but any social network knows that drastic changes come with risks. Just look at Friendster, a site that fizzled after changes to the interface and a subsequent exodus made it less valuable to users.

In early February 2013,  Eli Janetis of Florida invited his friends on Facebook to join an event called “A Random Act of Kindness." His friend Matt Scheidt of Winston-Salem accepted the invitation and became the administrator.

The "graph search" feature, which will let users comb their friends' pages for everything from travel tips to restaurants they like, gives the company a path to grow its revenue but could also add to privacy concerns. Most analysts don't see the new feature as a direct threat to Google — for now.

The wildly popular photo-sharing site Instagram nearly caused a user revolt when it revamped its terms of service and privacy policy to suggest it could allow uploaded photos to be used in ads without users' permission. Instagram later clarified its position in an effort to quell concerns.