Cool article. I found some neat things in their data.
You can see the burning man "city" moves slightly each year creating an "echo" in the data.
https://labs.strava.com/heatmap/#13.49/-119.20399/40.78672/h...
Also, some people appear to have biked to the Farallone's https://labs.strava.com/heatmap/#12.41/-122.97170/37.71310/h...