$1b is a steal for Yammer. I'm surprised Yammer would take that right now considering it's current valuation and how bright its prospects are. It has one of the most efficient B2B customer acquisition schemes. Even with the culture mis-match, I suspect this will be a good acquisition for MSFT.
The Facebook IPO punched a temporary hole in their valuation. I think Microsoft got a modest steal due to that.
Yammer has already won their segment. Imagine owning a private corporate social network, spanning the globe, with paying clients. It's an extremely valuable segment.
Depends on how narrowly they define their segment. I've done a ton of customer development interviews with people over the past 8 or 9 months, exploring this whole "enterprise 2.0" space, and I've found that - by and large - most people haven't even heard of Yammer (or Jive, or Broadvision, or Lotus Connections, etc). My perception is that anyone playing in this space isn't even really competing with Yammer (or Jive or whoever) they're competing to convert current non-users of this kind of technology.
