i can Think of a billion other thing people can do that is worse than playing Pokemon GO, people goes outside and meet other people. Seems like they have a lot of fun. i really dont see any harm in that. of course there are those who takes it a bit too far but most people can handle it.
I tried it and got bored after 5 minutes and im not surprised if the hype fade away and most people quit. but let them have their fun.