Matt o' blackbeltjones makes a response about conversation interfaces, and: "the resurgence of popularity of what amounts to the command-line interface, especially amongst younger people, due to SMS and instant messenging."
They're two quite different things I think. I could see IM being used in both command line and conversational capacities, at seperate times. (Come to that, are there any good command line equivalents available by IM? How about piping information from bot to bot?)
The command line, because of its context, is very obviously an abstraction onto a computer, and it's critical to learn a new grammar to communicate. An IM client, because of it's context, is at face value only an abstraction to a human/human conversation. There's a difficulty here in that people expect a greater level of intelligence and understanding -- but there's also attributes that make the job easier. For example, it's okay to say "I don't understand". Also, people are familiar with scripted conversations, from telephone callcentres and the like. I can see a command line being extremely useful over IM, but I can also see a conversational interface being something different and useful in it's own way.
I was thinking earlier about how to storyboard conversations. If it's a standard flowchart, or graph: A node, or state, can be a point at which the bot returns information or asks a question. Arcs are various user responses. So far, so www. What the conversational interface allows is arcs to shortcut nodes by giving more complex responses. [I'm modelling all of this internally with maps, according to the sameness of interfaces.] And this allows for long-term more complex interfaces. As the landscape is explored and more keywords are learned by the user, shortcut arcs from what were ostensibly simple nodes can be discovered. This is something that can't be done on the www without altering the pages and disrupting the familiar interface. Another difference is that obvious unambiguity can be used in the interface to hint at shortcuts -- on the www, the hierarchy is not a beast easily disturbed.