The article mentions how SMS texting is the preferred way of sexting for most. I'm not sure about the US but I'm from Singapore and here, WhatsApp and other similar IM apps have far overtaken SMS in terms of usage. This changes the texting dynamic somewhat because these apps often report whether the other person is in the midst of typing a message or has read your message. Thus, you can get a far better idea of what the other person is thinking about. For example, someone who types, deletes, retypes something multiple times before finally sending it probably is far more interested than they might otherwise let on.