Originally Posted by
boberonicus
But in Google's defense, the default setting is to display images for trusted senders although I'm not sure what that means..
In the help, it seems to indicate that anyone is trusted if Google's spam filters don't flag them as spammers/malware distributors.
And yes, images frequently contain user-specific urls. This doesn't change the tracking; it just hides your IP. People sending these won't see your IP when they look who downloaded it. They'll see that (for example) gfunkdave downloaded the image from a Google server.