Search engines create profiles based on your ip/search history. In fact there's been some research on how many profiles get created on a brand new search/ip combo and it's loads. It was something like 12 profiles within a minute last time I looked.

Those profiles are then used to market (not that harmful) but also categorize you and in cases limit how much credit you can use at a store or what the price they show you (hotels/airlines) is...

That small change can return a lot of privacy.