In person, participating in a conversation doesn't cost much.  It only costs a few seconds of my time to participate in a conversation in the hallway, so I don't mind shooting the breeze about things I don't really care about like the Red Sox (hehe, I know, this is heresy in Boston, please don't stone me! :)  But when not in person, the time premium associated with participation rises considerably.  Even reading what the conversation is about takes time.  I forward all email that I'm only cc'd on into a "special" file that only gets reviewed as needed.  I rarely need to.  (Now watch, that trick will no longer work).

Contributing to an online conversation takes work.  I have to fully understand the context of the conversation before I can even begin to formulate something intelligent to add.  If I want to write a blog post about it I also need to have a blog set up first, and if I want to leave a comment I usually need an account on the site I'm using.  In order from most expensive to least expensive, these are the ways I can think of to participate in an online conversation:

1. Writing a book
2. Writing a magazine article
3. Writing a blog post
4. Writing a comment
5. Writing a tweet
6. Clicking a button

There are others, of course, like leaving a video response or a podcast, but these are the most common.  One of the great things about the Web 2.0 phenomenon is that it caused developers to focus on making the user interface so transparent (usable) that each of these ways to participate became easier and easier.  The participation premium got lower and lower.  Before Blogger, setting up a blog required you to do a lot of legwork around hosting and software setup.  Before Digg, you had to actually write something in order to contribute to the conversation, you couldn't just click a button to say whether you agree or disagree with something.

Software usability is really a euphemism for transparency.  There is an idea behind each element of the user interface, but if the user has to stare at it and wonder what it does, and maybe mouse-over it hoping for a hint of some kind, the developer has failed then and there to make the user interface "usable".  Usability is inverse to the amount of time the user spends thinking about it.

For example, I've been playing with an XMPP client lately.  It has TONS of features, and it's really great in that department.  But it exposes all of them in the interface.  And so trying to send a message makes me stop and think about all of those capabilities before sending the message.  It takes at least twice as long as a tweet.  So I don't use it.  The time premium is too high.  (BTW anyone know of a good XMPP client for Windows?)

I like the idea of Twitter because I don't invest much in using it--I have a thought, and out it goes.  I don't even spend much time proofreading it, because the thoughts I express via Twitter usually aren't worth it.  If they are, that thought turns into a blog post, like this one :)

It's funny how insignificant usability seems at times.  It's usually an afterthought in the software development process, yet I've seen it sell software time over time.  Everyone should--and does, at a subconscious level, I suppse--strive to seek out the tools that lower the conversation premium the most.  It's the reason Apple does so well with its hardware.  Not only does it make life more pleasant, it also encourages us to participate more than before.  It also makes the software companies that sell those tools a great deal of money.