I think you hit it at the end there. A friend of mine recently said to me that the most interesting thing about Twitter is that they're the first major web property to outsource the interface development. Twitter is as simple as the designers who actually the stuff people interact with Twitter through. If all you use it for is sending status updates via your mobile Twitter couldn't be more simple: You save a phone number and send a message.

Calls for simplicity are almost always empty rhetoric. "Make it simple" is no more guidance than "make it good." Twitter is absolutely simple. As noah said, if all you use it for is sending status updates then it couldn't be more simple. But that simplicity is always contextualized. The user has to be comfortable with social networks, with user profiles, following (friending, subscribing whatever) before it can make any sense. Strip that away and it fells more complex. Keep going, make the user less comfortable with the web in general, with web forms, clicking, turning on the computer, and the complexity grows and grows. The question is what you granted, does it do a task simply? And i think it absolutely does.

As far as @replies, #hashtags and re-tweets, (or more fringe ideas like http://twitterdata.org/) can all be handled in the client. I don't think it is a matter of pushing complexity to the API, the API remains very simple. The keys is to design apps that behave as resources, as public utilities. (A point made more clear by the events of this week.) We get water through the tap and can do any damn thing we want with it. If it is dirty, you buy a filter, warm? add ice. And this is the potential with something like Twitter. They stay exactly the same, let people do whatever the hell they want. And if people don't like seeing #hashtags in statuses, there is a client for that (the brita filter), want to view replies as a conversation? there is a client for that. And so on. Twitter's complexity mirrors our complexity, our mis-use and re-use of language and tools. Would anyone buy a hammer specifically designed so it can do nothing but drive nails?

your last paragraph makes perfect sense, though from the experience of the user, perhaps Twitter is neither simple nor complicated, but modular - it allows users to choose their desired degree of complexity. (and perhaps THIS has something to do with how it got to where it is....)

in that sense, I might shift from an analogy to a hammer (there are many types of hammers, but there are not many types of Twitter, and hammers are all used in the same way) to an analogy with a swiss army knife (use only the standard knife vs. all the implements) or even a laptop (use pre-installed software programs vs. add more), i.e. something that can be used in a range from simple to complex, depending on the preferences of the user.

Perhaps jumping on your hammer metaphor is missing the point, but perhaps not--my quibble with your tweople-rousing generalization of a title is that I think Twitter begins with something simple (status updates, as Noah pointed out), but can then evolve into all sorts of things depending on how much you let yourself tumble down the proverbial rabbit hole. I liked Stephanie's Swiss Army knife comparison because I think we can infer from that Sysomos tweetstat pr0n making the rounds that most Twitter users just use the blade, as it were.

What I'm really interested to see, though, is how well Twitter can resist scope creep given how facebook keeps gobbling their territory, with the news-feed-centric redesign, username URL's, and so forth. Is the appearance of godforsaken games like Spy vs. Spy on Twitter the beginning of the end?

@ Nate

"What I'm really interested to see, though, is how well Twitter can resist scope creep given how facebook keeps gobbling their territory, with the news-feed-centric redesign, username URL's, and so forth. Is the appearance of godforsaken games like Spy vs. Spy on Twitter the beginning of the end?"

This, I think, is the crux of it. From what I understand, they're leaning toward being light on the scope creep, but the changes being contemplated are definitely beyond "status." Even calling it status is sorta disingenuous. It was always more than status.

See, I think EACH INDIVIDUAL USE of twitter is still very simple. But there are tons of them, leading to a complex system. I'd say it's like having a regular hammer, a picturehanging hammer, a jackhammer and a mallet all in the same box marked "hammer."

your metaphor is upside down. It would be one hammer that people are using to build houses, hang pictures, tear down walls and bang out morse code messages with. A box labeled "hammer" is facebook, not twitter.

Can you unpack your claim that "It was always more than status?" What else was it? Specifically? Social networking sure. But looking at twitter as a tool, how was it more?

Well, it was more like a "what's on your mind." Pontificating. Link sharing.