I'm back to thinking about CSRF: why is it useful for sites to be able to embed resources (like <img src="othersite.com/whatever.jpg">) and for the browser to send the user's cookies to the third-party site?

There's "ads" and "tracking" obviously but I feel like there's another actually-useful-to-users reason I'm not thinking of

@b0rk
Maybe badge sort of things where it shows a different image depending on user info, like an image button for subscribing/unsubscribing that shows whether you're currently subscribed (for another service like Facebook, YouTube, etc.)