Twitter's growing faster than you think

I recently told my friend Lane Becker that I didn't think Twitter was growing much anymore. I was wrong

Twitter's growing at a very healthy rate. And in this case, the compete numbers, even if absolutely correct, don't tell the whole story. The first thing any serious twitter user does is download a desktop client, or start using TwitterIm or Hahlo and being relying on the Twitter API, whose usage isn't reflected in Compete statistics. So the Twitter growth is really a measure of some baseline passive users, and the flux of new users entering the system, which means that Twitter's attracting a linear number of users each month, or better.

Congrats to Twitter. Now can someone please explain what Twitter is to all my friends, because I'm failing at it.