One of the key reasons whatsApp was successful was the simplicity for the user to start communicating - No registration or username creation hence allowing users not to care about remembering passwords. Another important feature was that the user did not have to search for their friends in family if they were on whatsapp and then add them or send request etc. They used the phone number and users phone book. If you have a friend uses whatsapp it will automatically show you.

WhatsApps is easy, simple, quick and beautiful! so the path to $16B exit is not a J2ME app but an idea to get users start communicating with minimum amount of effort and time.