A trip to the ER with your phone may mean injury lawyer ads for weeks http://arstechnica.com/tech-policy/2018/05/injury-lawyers-push-ads-to-patients-phones-when-they-go-to-geofenced-ers/ … by @BethMarieMole
They can sell your phone number's location, but linking that to your browser takes more work. Major carriers have a service that lets ad networks do that with a deeply buried opt-out setting. Never browsing directly from your mobile connection (eg using vpn) stops it too.