Google Personalized Search

A while back, I wrote about Google now having a search history. Well, now, they are experimenting with tightening up an individual's search, based on what they have searched for before. This is called Google Personalized Search.

This is kind of a grand experiment, and I'm not really sure if it's a good idea. I have a search history going, and it's all over the map, searching for all kinds of different things over the last month or so. But, when I search, do I want my search limited by what I searched for before?

If I was researching with books, would I want to keep looking for my information in the same isle? Or would I want to search the whole library?

I don't think anyone really knows if this will help someone have a better search, but without some serious testing, how does anyone know? As always, I'm impressed that Google keeps trying to make things better...