Some people (especially teens) get so much addicted to cell phones for talking, video, messaging, games, etc that they forget the real purpose of the phone and waste large part of their time in unnecessary interaction over their cell phones.
Nothing more can be a distraction for a teached in the classroom, when a student's phone rings. Cell phones are increasingly becoming a problem for the schools during classroom hours and are becoming a means of cheating during examinations and other kinds of ability tests. All this is really bad and does hurt the future of the student, who doesn't realize that he/she is him/her-self responsible for it.
Health of those living in the vicinity of cell phone towers is becoming a growing concern. Towers result into an area with concrete development along with destruction of natural features (vegetation etc) around the place. The towers also emit strong electromagnetic signals, which can be health hazard for those living nearby and who are getting exposed to strong radiations continuously during a good span of their lives.
While remaining in touch is good thing but sometimes it becomes annoying to have to deal with continuous incoming phone calls. You are on a vacation and your boss calls up, how does that sound!
Cell phone monthly bills are usually more than a landline bill. Sometimes, we may not require to have a cell phone but we still buy one and start paying monthly bills; so it increases our monthly/recurring expenses.
Use of hands-free (wired/blue-tooth) can at times pass on loud sounds to our ears which can result in weakening of ear-drums. Nowadays, one can download lot's of songs, so keeping the hands-free glued inside your ears for long hours can really affect the sensitivity of ears in the long run of life.
There have been cases of cell phone blasts, due to the excessive heating up of it's battery. This can be a fatal issue; although rare.
No joke, the surface of a cell phone has millions