If you know Facebook’s “Mini-Feed” updates—short updates about what friends are doing—Twitter is built around the same principle:  What are you doing?  Users sending tweets via SMS and the Web are typically trying to impress or amuse their friends with exploits and observations.  This may seem like trivial fodder (and, mostly, it is), and that is precisely why tweets matter.  It’s about “getting some new.”

Consider a typical moment in front of your computer:  You either (a) tackle a complex project, (b) write a thoughtful, proactive note to a colleague or (c) check email and other inboxes.  Face it:  Option “c” wins most of the time, because of its passive nature and your hope for “some new” as each message arrives.  This is human nature and has made email the most popular online activity for decades.  Twitter combines the filter of social networking (those you know), the brevity of SMS (140 characters) and the guiltless frequency to update as often as you like—there’s no such thing as spam in tweeterland.  Only those who ask are updated with others’ tweets; it’s a social contract via the Web and wireless devices.  If you don’t care about what people whom you know are doing, then well, what are you doing?

Also important is that Twitter is an “ingredient service,” less a destination service.  To use MySpace meant visiting the site and managing one’s profile via PC-based browser (only).  To use Facebook means a combination of Web-based visitation and via Blackberry/iPhone—progress for sure —and Facebook’s Mini-Feed feature was likely critical in Facebook’s ability to surpass MySpace in global unique visitors this April (per comScore).  Twitter goes a step farther in that users use Twitter to update Facebook and other social networks; it’s a service that’s meta to others.  Put another way:  The more flexible and lightweight the experience with a social network becomes, the more popular the service gets. Um, duh.

Whether you realize it, it’s increasingly popular to update your Facebook Mini-Feed using Twitter.  This means that sending one SMS message updates Twitter, updates Facebook and perhaps updates other social networks (e.g., FriendFeed).  If all of that sounds really complicated, I would say you’ve hereby reached a “get over it moment” and expect more-not-less complexity in terms of managing multiple social networks.  Of course, these services do have an obligation to provide simpler ways in which to tie them together, or those that fail to do so will be made irrelevant or insolvent.

Wait, how does Twitter make money?  How do I know it will stick around?  You don’t and it doesn’t matter.  Twitter and the act of tweeting have hatched, and like Napster, the demise of the company does not necessarily lead to the demise of the behavior.  In fact, truly great Web legacies grow to several times the size of the company that created them, as happened with file sharing.  Also growing in popularity are the “Twitter for [insert market]” companies.  Tumblr is like Twitter, adding richer multimedia capabilities.  Blip.fm is like Twitter, with a music-specific focus.  A recent conference in San Francisco called TechCrunch50 awarded its top prize to Yammer, a “Twitter for companies.”

So jump right in, it takes about three minutes to get started.  Use tweet in a sentence over the next two weeks.  It will feel uncomfortable at first, but it will matter.  Shoot a tweet to @cphenner to let me know if you agree—just keep it to 140 characters.