Due to what then?

Launch rollout: "Here's a collaborative engine, to help you work and interact with others. Others who likely won't be able to use the product, because we'll make invitations rarer than six-leaf clovers until we pronounce 'failure to launch', kill the product, and then open it up more."

Bad rollout (invite only) and marketing. They generated a lot of hype and then kept people from using it until interest died off again.