Strong disagree; most of the Matasano people who use Campfire have little or no exposure to other 37signals products.
It's just a very solid, inexpensive private web chat that we don't have to host ourselves. It works everywhere, unlike IRC, SILC, and AIM, which almost everyone filters. It is completely brilliant for conducting meetings. We're all smart people; could we have built a substitute? Sure, if we wanted to be in the chat business.
Fair enough, although it raises the question - is its obscurity its entire comparative advantage? I suppose additionally, since it is a paid product (with the free version having severe limitations) it is unlikely to be popular enough to draw the ire of the IT folks, and everyone has a client installed already (browser).
It's just a very solid, inexpensive private web chat that we don't have to host ourselves. It works everywhere, unlike IRC, SILC, and AIM, which almost everyone filters. It is completely brilliant for conducting meetings. We're all smart people; could we have built a substitute? Sure, if we wanted to be in the chat business.