It's an interesting question to consider, especially if you consider just how many Google services you might use: Gmail, Reader, Maps, GTalk, YouTube, Latitude, Calendar, Contacts and, oh yeah, Search. Dashboard shows you everything Google knows about you.
It shows your most recent searches, last conversations in Google Talk, most recent location — basically, it summarises all of the info you have poured into every Google service you use, so you can see it at glance. It's kind of startling actually. From the Dashboard you can drill down into every app to look at the info more closely or adjust privacy settings, which you certainly might feel inclined to do. Or it might make you want to unplug from the internet entirely. [Google via Lifehacker]