I think using a cell phone or i-phone in public should be consider a social tabu. Find a spot away from the public to talk or text.
Texting while driving... Sure that should be illegal with very strong penalties. But looking at your phone while your sitting on a park bench?
You sound like a nanny-stater.
No. Cell phone use on a park bench is fine. There are social signs that people give off that indicate to me that they are people with whom it would be wholly unproductive to speak. Cell phone use while out and about and backwards caps on heads are such signs.