I've been thinking for some time about this piece Emily Nussbaum wrote on Mad Men where she articulates the basic problems with the sixth season and, perhaps now, the entire series:
As the island was to "Lost," Don Draper is to "Mad Men." He was a great premise, a mystery we were dying to understand. But, the more the puzzle has been filled in, the more he's begun to feel suspiciously like a symbol, a thesis title rather than a character: "Appearance Versus Reality"; "American Masculinity as Performance"; "The Links Between Prostitution, Marriage, and the Ad Game." I'd hoped that the death of Don's California-stoner muse, Anna, two seasons ago—in one of the series' standout episodes, "The Suitcase"—would work as an exorcism, but instead Weiner doubled down, adding fresh flashbacks, to the point that even JT LeRoy might think that he was laying it on a bit thick.
To recap: Don's real name is Dick Whitman. His prostitute mother died in childbirth; his dad, her john, beat him. His fundamentalist stepmother called him a "whore's child." Then his father got kicked in the head by a horse, and the stepmother moved in with her sister, herself a prostitute, living in a brothel. The stepmother, heavily pregnant with Don's half brother, prostituted herself to her brother-in-law, as the teen-age Don knelt outside her door. He watched them, through the keyhole, have sex. C'mon, now. This is no longer the backstory of a serial adulterer; it's the backstory of a serial killer.
We haven't even got to the part where Whitman goes to fight in Korea, accidentally blows up his superior officer, Don Draper, steals his identity, forms a secret relationship with his widow (she's motherly, yet also somewhat prostitute-like, since he pays for her upkeep), becomes a greaser, and seduces a model who is also concerned primarily with appearances. Eventually, he gets into advertising, and when his half brother, Adam, finds him, Don rejects him, and Adam hangs himself. It's not that none of this makes sense, or could make sense; it's just too much, overdetermined. None of the other characters has this sort of reverse-engineered psychology, and for good reason: it's a lazy way to impose meaning.
Reading Emily detail Draper's back-story, I had the feeling that I'd seen this improbable twisting and turning before—in comic books. We grant comic books that license because they are arched over decades, forged by different writers and editors. Some writers emphasize one aspect of backstory more than others, and whole events are often retconned into oblivion. Either way I don't think backstory is so much the problem, as the belief that backstory has more explanatory power than it actually does.
We are being told that Don is having an affair with Sylvia. Presumably this affair has some relation to the perversions he experienced as a child. That's a good start but it is insufficient. Why—specifically—Sylvia? Who is she? What, precisely, is she offering that Don simply can't get enough of? How does that particular character interact with whatever is going on in Don Draper's head?