Her decision has been a long time coming, and may be necessary. I mean, people didn't job-hop in the 1960s the way they do now, but advertising was its own animal, and as a career decision this was probably one hundred percent right.
Here's the thing: in business, you sell yourself. Ted Chauogh wants to hire Don's protégé, and he negotiates with Peggy over price and title. It's not sexual; Peggy's gender is not part of the transaction. Yet the negotiation perfectly parallels what Joan did with a percentage and a partnership. We all do sell ourselves for work, for ambition, to succeed.
Certainly a lot of feminist and other theory would tell us it's all prostitution: Marriage, dating, Valentine's Day, casting couches, and every other transaction in which men are the buyers. But when we look at it that way, we can forget how painful this particular act of prostitution is for Joan, and let's not forget that. Last episode we saw her say she has some control at work, and how important that's been for her. This wasn't just a sexual transaction, it was one that stripped Joan of her sense of control, of self-ownership, and left a dark place behind her eyes, brilliant portrayed by Christina Hendricks.
Meanwhile, Peggy sacrificed love for ambition, because truly, she and Don love each other: Watch him kiss her hand, and her choke up in response:
This clip parallels the end of Episode 4.07: The Suitcase. Don kisses the hand that he held then, he honors the love they share. But as Roger said last episode, it's every man for himself, there can be no loyalty in business.
Some additional thoughts:
Deborah Lipp is the co-owner of Basket of Kisses, whose motto is "smart discussion about smart television." She is the author of six books, including "The Ultimate James Bond Fan Book."