The radio frequency from cell phones can cause brain damage or cancer. It also keeps people away from interacting and socializing. Also cell phones are the reason why there is something called 'cyber bullying' Another disappointing fact is that even if people meet up at someone's house the first thing most people do is check for wifi connection.
I just think cellphones are slowly making people get distant with other humans. People are slowly becoming anti social and that is a danger to our species. If we have the gift to interact with others of our kind, we need to take advantage of that. I believe that phones will turn us into the worst species one day.
Cell phones are an obvious benefit to society, not a danger. The biggest danger to society that a cell phone poses is that it "could" cause cancer, but there are many things that could cause cancer. Cell phones benefit us by making communication easier, quicker access to information, and plent of other things.