I wonder what this means for computer vision startups like http://clarifai.com ? Its hard to compete with Google on a task like image classification when Google has immense computational resources, tons of data, and hoards of top researchers.
Forget new services, even a small change in their existing products by Google can destroy lot of companies. Everyone remembers how they ruined email marketing by caching gmail images.
When you open an email with images, Google will proxy the request for the tracking image and then cache it. If each user has a unique tracking image, you know when it was opened. Google is not caching the images before the open so you do know that it was opened.
What you possibly lose is repeat opens which might end up with the cached image.
That seems like a loss, but with this change, Google turned on images by default. So you get loads of Gmail users loading images by default rather than the old way where many more people would be loading your message with images off.
MailChimp has a little write-up about it: https://blog.mailchimp.com/how-gmails-image-caching-affects-...
tl;dr: Google's change didn't stop marketers from knowing you opened the email, but did potentially block cookie sending, IP address information, referrer information, etc.