Who is "they"? My Wifi access point doesn't indicate if I'm home or not. And if someone buys an iOS powered device, it specificially asks about using location features (where wifi locating would be used, along with cell towers and gps in appropriately equipped units). If its off, no one knows. If its on, only the services the person chooses knows the location, and it's only easily accessible if the user chooses to post location somewhere. This stuff all defaults to off and forces the user to make an active choice to turn it on.

Sure, with cell tower info, it's somewhat easy for the phone company to know where someone is, especially with E911 laws mandating this. But that's separate from wifi, and has been a general "concern" since cell phones existed, due to how they have to work. Or really any radio transmitter in general. And sure, someone local could have the right radio scanning equipment and use it to track my phone. I accept this as a minor risk to have the convenience of a phone usable nearly anywhere.