I want an IM messaging product where I can communicate with almost anyone...
Disadvantages of SMS is that it is tied to a phone number (no privacy) and is expensive in most of the world. These are not issues with messaging but it does suffer from not having a standard protocol that everyone can use like SMS.
SMS is stuck where it is at now but it's certainly possible for messaging to be much more then it is now.
- Crossing a border with SMS is rather expensive. Only recently that T-mobile finally dropping 35 cents charge for international SMSes, not sure about others...
- UTF-8 implementation sucked until recently. I think it is still unpredictable if it cross carrier.
- Group SMS is non-existant, although MMS can handles it. (and if you have someone uses sonething like Google Voice, forget group messaging... although it is probably Google Voice who would deserve some blames.) But there is no way to get receipients' capabilities.
In Europe we have pre-paid packages with flat rate SMS.
Other than some carriers offering extra international SMS options, it's certainly not is a standard.
I am not very sure about how it really works in Europe, but I have feeling that EU countries have more comprehensive arrangements for calling/texting/roaming across their borders, or at least I wouldn't be too surprising even if so.
The option depends per operator.
No phone number, email, or username required to connect with anyone, anywhere.