Creepy. I’m having the urge to learn how to write Android apps just so I can write a firewall to defeat this.
Everything associated with Google is creepy.
Google is Evil.
I'll buy that for a dollar!
If you're using Gmail (to receive email, as opposed to sending and tracking using the Streak plugin), you probably want to choose not to show images automatically.
It used to be that Gmail would always require confirmation before showing images, except for ones from white-listed senders. But last November, they introduced a new "feature", whereby images are now shown by default. However, a Google server proxies the image fetch. That keeps the sender from learning your IP address and doing certain other nefarious things (images are also scanned for viruses), but, because Google's proxy doesn't fetch until you open, the sender still gets to know whether and when you opened the email. Unless you follow the instructions at the above link to disable the new "feature".