This is what Google does. What you search is becoming a better and better predictor of what you will do. Most searches are based on future plans, purchase, or interests. They even know your current and future locations if you use google maps for directions. If you use gmail, Google can tell that you just broke up with your girlfriend, or are graduating college.
Sidenote: we don't "give away" this information. We exchange it for the value of the information we are searching for. Microsoft has even experimented with paying people (with discounts) to use Bing's product search features.