There is value in buying into a network of users, but it is in no way worth 100X multiples of sales. Since such deals usually happen within the Silicon Valley e

There is value in buying into a network of users, but it is in no way worth 100X multiples of sales. Since such deals usually happen within the Silicon Valley ecosystem, I strongly suspect that cronyism is involved. VCs in Yahoo decide to do the VCs in Tumblr a solid, and the favour probably returned in the future. This is what investors really mean when they tell companies that they have 'connections.' The VC business is tough, with average returns dwindling each year since the bubble, so there is motivation for this sort of thing to happen.