The sheer amount of categorized, identifiable data with Google.
If you think I am taking this relaxed weekend to indulge in favorite pastime - Google Bashing, well, you are probably right BUT my passion for bashing google does not mean what I say is wrong.
If you want to be scared and/or shocked head over to : www.google.com/history
Type in your google password and see a list of ALL the search queries you have ever made on Google. ALL of them. Even the naughty ones.
You can see statistics of your searches per month, per day and infact even by the hour. The graph here is my search statistic for this past week. Do post your "scores" so we can see who searches the MOST :)
Go check this out. You will find that Google now knows more about you than even you do.
Be scared. Be VERY scared.