Google knows who you are:
Someone recently tried to use an application to sign in to your Google Account, email@example.com. We prevented the sign-in attempt in case this was a hijacker trying to access your account. Please review the details of the sign-in attempt:
Wednesday, August 22, 2012 10:08:53 AM GMT
IP Address: 18.104.22.168 (vodafone.de)
Location: Stendal, Germany
The solution, Google says, is for me to change my password. Problem is that in this single-signon (and leave automatically signed in) world, I would have to arrange to change the password in dozens of areas: multiple Web browsers on my many computers, including Android phone and tablets.
People recoiled when Microsoft first suggested a single login (and password) for all its properties. Google was much more sly: first just for GMail, and then slowly it brought the water to boil spreading the single UID to eventually all its properties -- without us frogs particularly noticing.
Even before this German attempted to break into my Google account, I had thought of changing my password (it is fairly robust already), and then realized just how long the task would take.