I've seen it being used.

Like on the frontend side with Facebook which thinks if I'm interested into cycling I will also be interested in cars (both are on the street, right?) or if I'm interested in some more dirty humor I also want to see more "naughty" stuff.

And also on the backend used by magazines and they mostly don't use the user profiles because it's too targeted and doesn't have enough audience. And if you make the targeting broad enough you'll have again people interested in chocolate so you target them with wine and whiskey.

Or even better on Amazon where you can buy a new TV and when you have done so it will suggest you even more TVs for the next months.