Facebook has nice email notifications whenever a friend comments on your status, sends you a message, or a variety of other reasons. The emails have subjects similar to 'John Doe commented on your wall post.' The unfortunate thing is that this email also appears to contain John Doe's (or your other friend's) IP address.
The email headers contain a line similar to:
X-Facebook: from zuckmail ([MTAuMzAuNDcuMjAw])
Copy this line out and feed it to this page:
You will get the IP address of your friend and clicking on it will get a geolocation-based map. This will also show you if your friend used their cell phone to post and who they use as their service provider.
This information is great when a fugitive is taunting law enforcement through their Facebook page, but not when a wife is trying to hide from an abusive husband and assumes Facebook is the best form of communication.
This isn't the end of the world compared to some of Facebook's other privacy problems, however, there is simply no need for Facebook to include these IP addresses and it should be quickly fixed.
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