Data would be interesting, but we'd also need to know what people think SMS is. For my mom, SMS is the text messaging app on her iPhone. My sister knows that it's iMessage, but she doesn't care, it's still the app that allows her to send a text message, it might be iMessage, it might be SMS, but practically speaking, it's a text message. My guess is that it could be IRC or ICQ for all she cares, it move a message from her to a friend or family member. The important part is that it's able to reach anyone with a phone.