How I Met Your Mother: "The Goat"

It's fallout time. Duck and cover, everybody.
So we had several theories espoused by faithful commenters about how the Barney-Robin thing would work out. Here's the rundown:
Theory number 1: One night stand. I'll attribute this one to scotteb, seconded by many.
Verdict: Certainly appears to be. Robin is determined to pretend it never happened, and does a much better job of it than Barney, who immediately develops a bad case of PTSD, jumping at every firecracker and backfire. It turns out his nervousness is due to his guilt at having violated the Bro Code, a longstanding collection of dude rules that includes "no sex with your bro's ex." There's no hint that Barney feels upset at actually … you know … feeling something for Robin. Not yet, anyway.
Theory number 2: Pairing up. JGabriel suggested that the logic of the show's premise demanded that all Ted's friends find partners before he finally gets together with Yellow Umbrella Girl (henceforth known as YUG).
Verdict: No pairing up in sight, I'm sorry to say. I scoured the episode for any sign that Barney and Robin remained vulnerable to each other's charms. I didn't see it. Did any of you?
JGabriel's pair-up logic got him worried that the show was going to start focusing on changing Barney from womanizing egomaniac to sympathetic mate. What was brilliant about tonight's episode was that the change in Barney didn't focus on Robin at all. It was his relationship to Ted that was put in jeopardy. Turns out that Ted understood Robin's reasons for sleeping with Barney. But he couldn't understand Barney's reasons for sleeping with Robin. And so another question that's been haunting the show all season long comes to a head: Is Barney any good for Ted? I've been arguing that the Barney influence on Ted is all negative — that the more Ted acts as Barney's bro, the uglier he becomes. It's rather sobering to hear that Ted agrees with me.
Theory number 3: Open relationship. Aspiring show runner Chrissy thought that Robin and Barney could hook up but have their own lives, returning to each other for companionship and comfort and eventual old-age cuddles.
Verdict: It was a truly creative idea, Chrissy, but it's nowhere in sight. Besides, do I want Robin to be openly promiscuous? She's confident professional woman and all, and as Ted says, we know she's dating, but the idea of an open relationship is all about "hey, let's have sex with anybody we want!", and I think it would really alter the way Robin's character comes across to have her define herself that way.