I look at it this way. Most of the questions about Kindles have been asked so there is not as much interaction. If you look though, you'll see some of the same topics repeated.
Check again when something new happens (firmware updates, new hacks, new Kindles, some other Amazon news, etc) and you'll see an explosion of activity. Most of us are lurking waiting for that next explosion.
Also, there are other places for Kindle owners to interact (Amazon's boards, Kindleboards...), so people are all over the place.