If you opt to publish your presence, other people can view a history of locations you've set and any status messages you've set. By default this is turned off.
To turn it on, go to your profile (click the "me!" text) and then select "profile and privacy". Tick the little "publish" box corresponding to presence, and click "save".
Note that only people who have access to your presence will be able to access your published log.
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