I guess that's why proven coders and proven commission salespeople (and proven accountants) can always find jobs, while "big picture" folks are left unemployed, wondering why companies can't see their brilliance. Or, if they're lucky, they sue Zuckerberg because he was able to do make an actual product which never got past the great-idea-over-beer phase for them.
(Ducks...)
Specifically, it's much more true in consumer than B2B. In B2B, biz dev is building partnerships, channels, distribution, obtaining resources you need at prices you can afford, all that good stuff. It's the absolute engine of your business.
If you're writing a B2C app, doesn't matter about the platform, then what biz is there to dev? In a similar sense, you need marketers, not salesmen, because your problem is getting a call-to-action out to your potential market as effectively and efficiently as possible. You can't do that door-to-door at scale.
But if you're doing enterprise software, the converse is true. You need biz dev to shape your proposition, and you need a sales force to go and hammer down doors and melt the copper in the phonelines.
Different problems, different solutions, different solvers, that's all.
We spent months and months building a business plan, doing market research, talking about our IP, our proprietary processes, etc. When talking to all the investors we met while in the Notre Dame McCloskey Business Competition, we were basically informed the business plan wasn't worth the paper it was printed on, we had no IP, and the reason investors won't sign an NDA on your idea is that an idea isn't worth shit. When I actually started building something, when we got the land needed for the other part of our business, and when we had substance (not just words); that's when they listened, offered us money, and things started to work out.
Edit: reading your other replies, it doesn't really sound like we're disagreeing.
I believe that it's just as valuable (i'm not going to say 'if not more')