Actually, iPhone is really useful location & time specific information gathering device. If you dont put your tweet,rss or any push notification apps (facebook included), than it realy enhance the way of life. I found it several times useful when i am looking for a book at bookstore and get very quick facts about the book.
The real dangerous device is iPad. From the day i have, i could not put it away. Its really content consuming device. My nights in my bed are no longer have the serenity of reading books but frenzy of consuming content channels.
Sometimes Gladwell's words keep coming to me: clearing big spaces of time. http://www.cbsnews.com/video/watch/?id=6058607n