It is interesting to note just how much data these sort of sites hold.
I lost track of an old school freind, after they moved house. We have been following our son on Strava, out in NZ. So I though I would see if my freind used the app too. Turned out he did and within two bike rides I had worked out exactly where he now lives, from the GPS tracks. Fine I am an old freind and he permitted my access to the data. But a hacker could do just the same.