What I don't understand is why Twitter hasn't been rewritten to be an IM system yet. Now's your chance. Twitter may never be more vulnerable than they are now.

What I don't understand is why Twitter hasn't been rewritten to be an IM system yet. Now's your chance. Twitter may never be more vulnerable than they are now. (Though you might want to consider that it will take you months to catch up to the enormous marketing advantage that Twitter got by building the "wrong" architecture first, using Rails.) But first, consider this use case: I hear that you belong to a certain IM system, so I go to the system's home page and type in your nickname. I'm presented with an up-to-date paged list of all the IMs you've ever sent, to anyone. I'm also presented with an up-to-date list of your followers (with cute little photos, all of which are up-to-date) and a list of those you follow, and by clicking any of their names I can get a list of all the IMs they have ever sent, to anyone. I'm not much of an IM user, so maybe I'm just naive... but I don't know of an IM system that does that. Perhaps because this idea is really expensive to scale, so nobody at (e.g.) America Online has ever bothered to try, because it wasn't evident that such a thing would be valuable until the folks at Twitter launched a quick Rails app to try out the idea.