The tragedy about this is that everyone involved here could have done something to avoid this except maybe EJ.
In order of culpability, here are the mistakes they made:
AirBnB's clearly inexperienced leadership has done a horrible job at communication. Sadly, this makes any real action they have taken to help the victim irrelevant to the public. Then again, their business has a fundamental risk, one of crime, which they seem unprepared to address or mitigate. Given their past resourcefulness, I have a feeling they will find ways to improve their product to make this less likely. I am not so sure about their ability to improve their communication.
Michael Arrington's job is to draw more eyeballs to TechCrunch and he invariably picks stoking controversy over responsible journalism. If it wasn't already clear to everyone including pg that he will do this at any cost, it should be now. Michael could have done some real journalism and talked to the police to find out more details, probed AirBnB for more details up front and may be even the victim on the one hand. On the other hand he should certainly have avoided comparing AirBnB to scamville, I don't think anyone thinks AirBnB is scamming users. But that's just who he is. He also takes great pleasure in calling people names. Notice that his latest post about pg has "Liar" emblazoned on the top. Can't say I expected any different, given his past behavior but at least pg will remove his blinders now that Arrington is treating him exactly like he treats non-luminaries.
The fact that PG had to jump into the public fray may have seemed inevitable given AirBnB's incompetent response, but it is almost always a bad tactic to have multiple people presenting the public face of a company. Even minor differences between what they say will be highlighted and will cause more confusion. PG even made the tactical mistake of responding emotionally to Arrington's "make the story more interesting without giving a shit about anyone else" approach, but in the long run this is a good thing. As I said, he'll now remove his blinders about Arrington.
EJ is not at fault except that she should have known that she was taking this risk when she rented her home to complete strangers sight unseen. This may be a flaw in AirBnB's model and their lack of focus on safety on their site, but if EJ had been my 6' 5" wrestler brother, I'd have waited a sufficient amount of time before giving him a knock upside the head and asking him what he expected when he handed over keys to an apartment that held all his belongings to a complete stranger while he was abroad. If EJ were my sister I'd tell her the same thing, minus the knock upside the head!