With that logic aspirin shouldn't be sold w/o prescription.
These kind of metrics have been available to the public for well over a decade. It's not new, just the way the device collects the data in a more transparent, less onerous fashion.
I meant that when Apple will provide this feature for the broad public in an easy way, people will use it a lot more then they do now. Thus my concern that people will 'overuse' it. Of course it's been out there for a long time, but we all know that when it becomes available in an easy, pre-installed app on the millions of iPhones it will be used by many.