GSM phone location can also be used to track other people than kids too. Friends, parents even pets. In Finland you have to give your permission if you want your cell phone to be located and who may use that information. Only exception are the parents "spying" on their kids.

Old people (with perhaps with dementia)can be located if they leave their homes. Injured hikers can be tracked from the woods. Some operators and phone makers provide phones for hunting dogs and other pets. If you can not find your dog, you can phone to it, the phone answers automatically and sends its location info to you.

Also games may utilize location info. Like It's Alive's BotFighters. (warning, site did not work very well with Mozilla Firebird, designed for IE.) See also their press release. Ads are not the only possible way to utilize the location info. There are many other possible services too.