> What's Google's motivation for this? Possibly, to get you to use more of their advertising services, which is in-line with lots of their recent changes (like

> What's Google's motivation for this? Possibly, to get you to use more of their advertising services, which is in-line with lots of their recent changes (like removing all organic shopping results in favor of paid listings, and adding e-mail ads to Gmail's promotion tab). Prior to this change, a dozen or so of Google's competitors offered e-mail remarketing. That's where you insert an image into your marketing mails to set a cookie in the recipient's browser when they open the mail, then you can later advertise to that person across the web. For example, you could show banners on the NY Times site advertising your Black Friday sales only to people that opened your Black Friday sale preview e-mail. With Google proxying images, regardless of cache/deduplication policy, only Google can sell e-mail remarketing to Gmail users now. They already sell web remarketing through AdWords/DoubleClick. That means companies advertising with Google's competitors will have to move money to Google.