Yes, it sounds pretty crazy. But it’s true. In the seed and series A, you are selling promise and some execution. In growth rounds, you are selling something that already “works”. You are selling a marketing machine, and the ability to “put in 1 dollar and get out 2″. In between, you are selling a hybrid of both, and that isn’t easy.
via Why The Series B is the “Sucker Round” – ROBGO.ORG.