The funniest thing about 37signals' Campfire coup is watching people trying to deny that it worked, or complaining about how
unfair it was. As if there was some sort of moral obligation to remain meek and silent in the face of your competition.
Many people seem obsessed with the fact that Campfire is so much easier to write than, say, Mathematica. And so it is, particularly after 37signals gave away the toolkit to do so. But if you're trying to make money with a chat app, building it is the least of your problems: There's probably thirty or forty chat apps sitting on Sourceforge right now. Your biggest problem is Metcalfe's Law: nobody wants to use a chat app which their friends aren't using. What you need is publicity. Ideally, you want to convince half the readers of Techcrunch to try out your chat app in the course of a single week.
Google handed 37signals that publicity on a plate, and they ran with it. Complaining about your product's imminent extinction at the hands of a mean, nasty corporate behemoth might be a good idea even if your competition is Microsoft -- obviously, your odds of getting those guys to back down are infinitesimal, but at least people might hear of your existence, it might be better to burn out than to fade away, and you never know: Maybe there will be room for more than one company in your product space, and if you play your PR cards right you might emerge with a reputation as the "classic", "alternative" brand and be able to ride Microsoft's coattails to fabulous wealth. Or modest wealth, anyway. This is how Apple Computer managed to stay alive long enough to be rescued by Steve Jobs.
But 37signals got extra lucky because their opponent was Google, which treasures its reputation as a kinder, gentler company that is certainly not mean like Microsoft, and is unwilling to tarnish that reputation over what (to them) is a simple demo app. So, when challenged, Google folded immediately and left 37signals in possession of the field. More importantly, Campfire is now a household word, at least in households where people read Techcrunch or Digg.
Meanwhile, you're welcome to try to compete with Campfire yourself. Bolt on features, make it do more, add plenty of nifty-looking toggle switches and a skinnable interface, make it scale so well that it runs on a netbook, etc. Go nuts. Don't skimp on the work if you don't want to: Work day and night! Just don't come crying when you can't make any headway in the market because it turns out you've been working on the wrong things.