My 'irrational' fear exists because of facebook's constantly changing uses of our data. When they began and we all started liking things we didn't know these same likes would be used for marketing purposes. We didn't know they would be used to sponsor ads. They went from a social network for people to a social network for companies. I agree with you and I do understand that I choose what is public, yes that's great; but how about the average user? Facebook makes money by selling it's users' data to companies. If everyone was private they wouldn't make any money.

This open graph search will be great for marketing purposes, and a silly tool for us users. I guarantee there are going to be some serious consequences of companies/governments having the power to instantly search and sort billion's of users' data. And maybe you'll say that some great findings can come from this search; maybe we can learn more about humans and societies with this tool? Maybe, but I believe the cost outweighs the benefits.