iMessage is free. It works on Macs, iPhones, iPods and iPads. I don't know what the usage stats are like, but those factors are probably worth a lot to teenage

iMessage is free. It works on Macs, iPhones, iPods and iPads. I don't know what the usage stats are like, but those factors are probably worth a lot to teenagers who either have to pay their own phone bills, or have to convince their parents to do it.