See http://pavelmachek.livejournal.com/120952.html - there's a valid point there. Given the sparsity of data on the map at https://location.services.mozilla.com/map it's possible to track individual movement patterns and things like road trips. Even just eyeballing the data there are patterns obvious to me, so somebody combining it with other sources of data could probably do much more. I realize that in practice this is unlikely to matter but it's the principle of the thing - leaking this kind of data is not Mozilla-y.
Thank you for the report. We are already tracking this problem in #961429.