Rule #1 in nerd blogging: jwz said it first. If you enjoyed The Enterprise, Apple, and Insufficient Ambition last week, you'll want to read Jamie Zawinski's essay that was so burned into my subconscious that I forgot it influenced me.
If you want to do something that's going to change the world, build software that people want to use instead of software that managers want to buy.
When words like "groupware" and "enterprise" start getting tossed around, you're doing the latter. You start adding features to satisfy line-items on some checklist that was constructed by interminable committee meetings among bureaucrats, and you're coding toward an externally-dictated product specification that maybe some company will want to buy a hundred "seats" of, but that nobody will ever love. With that kind of motivation, nobody will ever find it sexy. It won't make anyone happy....
So I said, narrow the focus. Your "use case" should be, there's a 22 year old college student living in the dorms. How will this software get him laid?
That got me a look like I had just sprouted a third head, but bear with me, because I think that it's not only crude but insightful. "How will this software get my users laid" should be on the minds of anyone writing social software (and these days, almost all software is social software).
"Social software" is about making it easy for people to do other things that make them happy: meeting, communicating, and hooking up.
Any more quoting than that, and it's just wholesale plagiarism. Go read the original, including the definition of "workflow".