Not sure why you think companies won't purchase Steem for sponsorship or ads in the future. The ad model will be different than traditional online advertising, but imagine any company can buy $1 million worth of Steem, probably be able to payout a few hundred a day a day or $100k/yr in rewards as blogger sponsorship or to promote their own posts. That's valuable. We're also not even including the payments/commerce part of the ecosystem. That's valuable too as well as the network effect.
RE: Where Does the Money in Steem Come From?