Actually that describes the original startup that Yammer was spun out of: a spam-heavy social network called Geni, that tries to turn a family tree int a social network, and brings not only your grandmother, but every other crazy distant relative out of the woodwork.

Very interesting. I'd never heard of Geni and the story behind Yammer.

Kudos to them for recognizing the value of an internal tool and spinning it off. Their original idea, Geni, seems to be languishing(unsurprisingly-how many mentally ill second cousins once-removed does it take to ruin a social network?).