I was sort of expecting there to be something in the article that wasn't in the title...
Don't they (37signals) have a collabortive web-based word processor of their own? It was called writepad or writeboard or something...
Yes, writeboard.com by 37signals. It's not real-time though. Something very much like SubEthaEdit but totally web-based is etherpad.com. I'd be interested to see a feature-to-feature comparison between SubEthaEdit and EtherPad.