Confusing opt-in and opt-out

Harvard Business Review posted a blog earlier this week suggesting that all businesses should treat email marketing as an opt-out process. Unfortunately, the post seemed to me to conflate and confuse a number of things.
She mixes in potential customers providing business cards to an exhibitor at a trade show with current customers that are using a product. She promotes businesses using opt-out as a default communication practice, but then talks about giving customers preference centers to manage the contact.
Overall, it was a very confusing article.
For instance the author says:

Many B2B marketers abide by a [opt-in only] policy, but they don’t have to — and shouldn’t. In fact, I’d argue, your business customers generally would prefer the reverse: an opt-out arrangement in which you send them messages unless they say “stop.”

Of course, the author then completely negates her own point by pointing out how businesses collect email addresses from customers and provide preference centers so that the recipients can control the communication center.

[T]he gold standard of business communications permissions today is to offer a choice to customers, like a web-based form that allows them to indicate their preferences. Let them choose the media channels they prefer and how often they want to hear from you. Allow them to change their preferences at any time. And above all, comply with their requests.

I dunno, that sounds pretty opt-in in practice to me. Once you get to the point of collecting email addresses from actual, paying customers, and implement them a preference center then I’m finding it hard to see how that is opt-out.
What a lot of other readers focused on and objected to is her example of collecting business cards at a trade show.

Consider this scenario: Say you attend a trade show and exchange business cards with an exhibitor. Does that exhibitor have permission to contact you by email? Of course. You fully expect to receive email (or phone, or postal mail) follow-up. That’s how you stay informed, build relationships, and do your job.

Many of us have had horrible experiences with over aggressive marketers collecting business cards and then adding us to marketing lists. A followup email or phone call is absolutely expected. An invite to join a mailing list? That’s not opt-out and is a fine practice. Adding every business card you find to your marketing list? That’s a major no-no and the only practice I’d consider opt-out here.
I am pleased to see the number of email marketing folks that commented at hbr.org, and on DJ Waldow’s post at Bronto blog arguing that opt-out was bad and even B2B marketers needed to use opt-in. But when I went back to the article to draft this post I couldn’t find where the author actually talked about opt-out marketing except when she said all businesses should use opt-out marketing. All of her examples involved users giving vendors their email addresses. How is that opt-out?