In some cases, yes I agree. But a chatroom is a pretty proven design. Scrolling output, user list on the right, input bar at the bottom.... and that's pretty much it. I doubt even 37signals would claim they designed that.

It's like IE complainging that firefox also has an address bar at the top, and back/forward/reload buttons.

If that was the case, why weren't there 100 other applications that looked just like Campfire prior to its release?