The pruned down list seems to be missing the very important "business development" role (which generally is mixed into other stuff.) Who's calling leads, creating deals, making contacts (substantial ones, not marketing-based ones) in the local business and technology community, understanding new feature requests, and basically making sure operating costs and revenue projections are on track?
I appreciate the call-out of an important omission from the article. I've learned that having a bizdev on the team is truly critical. That whacked me on the side of the head when I started thinking about Twitter's strategizing (http://www.techcrunch.com/2009/01/13/twitter-decides-to-hire...), and thinking about the shaping of various features that customers are not getting a chance to weigh in on. I've tried to wear the bizdev hat myself but it is all-consuming. Now I have a full-time bizdev partner and it's making a world of difference in focus/direction. The XP practice of "on-site customer" is really enabled by having bizdev pull the customers close early on.
Another valuable role I've discovered is that of the incubator (I'm not YC; doing OTBC in PDX). It's another secondary role similar to Lawyer, but can be very supportive in making sure you're focused on doing all the business stuff that hackers can easily lose sight of. I'm presently being shown the value of having a solid business plan, perfecting multi-length elevator pitches, and refining the more formal investor and sales pitches. This is all possible thanks to experienced entrepreneurial coaches who really want to see you succeed.
Lastly, the "consort" is a non-obvious role -- someone who can give validation to your thinking, and exchange predicament stories with you. You may find him through the incubator, or at a hacking event, or wherever. My main consort is an extremely capable hacker and our regular discussions are gold.
So with the core team containing the right hacking, creative, and outreach balance, you can make progress. But I want to stress that the supporting people (Lawyer, Consort, Coach, et al) provide a lot of necessary elements.
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.
