Last Thursday, a lot of new iPhone 4 users hit the scene. No doubt some of them were young adults, with parents in tow, to get on the iPhone train, refresh an older handset or replace a lost or broken device. But is that really the best thing? There’s been a lot of buzz recently over teens and cell phone use spanning everything from morality to safety.

Teens and phones have been a staple of American culture for decades. Those of us old enough to remember Marcia on The Brady Bunch gabbing on the line to girlfriends have those images etched into our brains. When cell phones went cheap and global, teens were there to snap up the technology and lead the vanguard of the newly birthed texting movement. In 2008, CBS found that 4 out of 5 teens had mobile phones. That number is sure to have risen since, as each year, more texting contests feature majority participation by teens competing for speed and accuracy. Last year’s LG U.S. National Texting Championship awarded a 15-year-old winner, Kate Moore, a $15,000 prize. Teary eyed, Moore said, “You’d never think a girl from Iowa would win something this big in New York.” (WSJ Blogs – Digits)  Well, I guess this thing is pretty big, Kate — maybe even bigger than you know. A Harris study released earlier this month showed that 47 percent of teens can text with their eyes closed!

Cell phone usage among this demographic has skyrocketed in recent years, partly due to the growing prevalence of smartphones. Slick apps, high-quality cameras, GPS, and video technology make smartphones a natural magnet for a group naturally wired to look for “cooler, faster, better.” But with teenagers so glued to their mobile tech, some troubling concerns are starting to be raised. According to a  Pew Research Center survey, teens are driving while texting in record numbers, with an alarming 26 percent admitting they text and drive. There are also other concerns about health risks. The Daily Green posted results of a Swedish study that looked at low-level radiation exposure from mobile devices. It found that people who started using them before the age of 20 were five times more likely to develop a rare brain cancer known as glioma.

As if health and safety issues weren’t enough, moral concerns plague parents of cell-toting teenagers. A joint study conducted by the National Campaign to Prevent Teen and Unplanned Pregnancy and CosmoGirl noted that a surprising 20 percent of teens and 33 percent of young adults have shared nude or semi-nude pictures of themselves online. Smartphones make this easier both technologically and logistically than ever before.

With all this disconcerting news, why would parents ever encourage or allow their kids to carry smartphones? Well, it seems there are positive effects of mobile technology too. Rapid Learning pointed to a surprising study done by Dr. Clare Wood of Coventry University, which found that kids who use “textism” — the abbreviated language of texting — show less difficulty than peers in spelling and understanding written language. Another recent Pew poll claims that smartphones can help bridge the digital divide between low-income minority students and higher-income white students, as lower-income kids can increasingly gain internet access through inexpensive handsets.

There are also more educational apps and mobile learning opportunities that are being developed. (Some teens are even starting to forego traditional “brick and mortar” colleges in favor of online universities, which are accessible on the go.) Some classrooms today are clearly torn over cell phones. Some use them creatively to stretch minds and encourage creative problem solving, while others chalk them up to distractions and ban them altogether.

Personally, I think mobile devices in themselves offer growth opportunities for young, developing minds. Have you ever witnessed a determined teen working out some tech problem with their device? Their tenacity and know-how is inspiring. Also, just owning and properly caring for this technological wonder might engender a little of that old-fashioned responsibility parents have been trying to instill for millennia. (Do we see any parallels to the honored institution of the teen owning their first car?)

What do you think? Are you a parent of a smartphone-using teen? Or do you forbid them for your kids? Parents, teens, or anyone else with a stake in the situation, let us know where you stand (or share your personal experience or wisdom) by commenting below.