I agree with Bitnetix - if I found out a cell provider I was using was actually handing out my location information to anyone other than a 911 center or other law enforcement for a legitimate purpose, I would be extremely upset with that company. In fact, I don't even want law enforcement to have it unless they can produce a court order, not because I'm doing anything illegal, but because it all starts to sound a bit too Orwellian to me.
Technology is such a double-edged sword - just because something CAN be done, doesn't mean it SHOULD be done. Think carefully about what capabilities you are giving to others, who may not use it in the way you intend. If nothing else, think back to when your were a teenager - even if you were a "good kid", would you really have wanted your parents to be able to track your whereabouts every second of the day?