There's a blurb about it on the Google home page, where the company often advertises various services and activities.
This is the first time I've seen this. Google is prompting people about the changes upon log-in now. I just went to log-in to Google Reader a few minutes ago, and was presented with the following screen:
I've logged in and out of Google services a number of times over the past week, and this is the first time I've seen this.
More coverage of Google’s privacy changes: