Twitter also lacks an income, but I digress.

One could argue that viral marketing is business development. The main difference is that in the former, your customers are doing the work for you, while in the latter, you've got a defined role.

I'd be careful to suggest though that this role isn't being done at all.

My only point is that he does not have a broader view in which bizdev is a super important role in and of itself.

I think the author is suggesting that the "Marketer" fulfills this specifically in the vertical he's approaching.