One of the key lessons of Web 2.0 is public by default promotes a healthy network of sharing in a way in a way tools engineering to be private by default never can.

But Twitter is about intimacy, and intimacy is largely unattainable (or at least elusive) in communication spaces without clear boundaries and memberships.

Which is a long way of saying I want "casual privacy" on Twitter, aka non-sequential, un-guessable URLs for status messages.

Status messages are currently an auto-incrementing integer. You can actually walk the entire update space with simple addition because there is a two part display key, identity + key, but if you were determined to you could walk the entire update space looking for all updates by a single user.

This means if you want to your updates private to only a group of approved friends, you need to mark them as private, and then Twitter will enforce this privacy if someone guesses (or finds) the permalink for an update.

However I might want to keep most of updates private (banal as they maybe) and still on occasion link to one to prove a point.

One way to accomplish this would be to add a private/public option, per update. That ways lies a fiddly mass of buttons and madness.

A better solution is un-guessable (before heat death of Twitter.com's servers at least) URLs, so my updates are nominally public, but un-discoverable without an explicit link made to them. (Which anyone who can see an update could do, namely me, or any of my contacts).  The downside, of course, is that links that I want to be private might inadvertantely get indexed by Search Engines, providing a false sense of security.  This could especially be a problem if the page is accessed by a user of one of the many Toolbars that capture visited links to submit them to search engines.

So, um, this is really a silly idea by a naive individual, so just forget it.

(p.s. this feature also really needs my much requested VisualIndicatorOfContactsPrivacySettings ala Flickr)