How deep is your data trail?

So I just cleared my Google search history.

I took a peek at my search log ahead of an interview with data privacy expert and Harvard Fellow Adam Tanner, and was simply stunned by the depth of my data trail.

Some companies say they collect user information to provide them with better services.

Tanner says, "They know where you live, work, go to university and they also know sensitive things like what religion you belong to - all with the goal of selling things to you."

As the saying goes, there's no such thing as a free lunch. And in this networked age, we're paying with our personal data.

But Tanner says, "There should be choice and transparency. You should know what you're getting into, and what you're getting in exchange."