Twitter is a very interesting phenomenon, that I have been following for a while now. It has a significant mobile component to it, so it fits my world. Actually, it is way more than just a mobile app. It is a mobile messaging app. And that's the space Funambol is in ;-)
Could Twitter be the answer to SMS?
I doubt it, but it is an interesting idea. SMS is about notifying people of events ("let's meet there") and having brief direct conversations ("what about lunch?"). Twitter is very similar. It is a notification engine (broadcast) and a point-to-point messaging platform (when you add @name).
What sets the two apart is the concept of following someone or being followed. Following someone means receiving every message that person sends out. This is where Twitter differentiates itself. It is a micro-blogging platform first, a messaging platform second.
And micro-blogging has its own problems. The number one issue, in my opinion, is what I call Twitter Diarrhea. It is an illness that attacks people that believe the world is really interested in everything they say. People that tweet every 10 minutes, tell you they are about to take a shower (like I care) and fill up your list of tweets in an hour.
The only defense against the disease is to stop following them. It is sad, because one of the 20 tweets is actually interesting. But when you have a "push" concept as in Twitter, message overload is a very significant challenge. In the last week, I stopped following at least five people I know well. Their interesting stuff / noise ratio was getting way too low.
When you move this into the mobile world, where you have limited real estate on screen and attention span (forget bandwidth, which is not a real issue with messaging), Twitter Diarrhea could actually be the outcome of a virus that infects the entire system, then tries to kill it.
It will be very interesting to see how the system reacts to it. And how it evolves to become a mobile messaging platform, if it will ever happen.