Jimmy Wales has made a lengthy statement regarding the Ryan Jordan (Essjay) situation. He has professed a lack of awareness of Jordan's misconduct, which given Wales is entirely to be expected. He has also called on Jordan to resign his positions of trust within the community. (No mention is made of his relationship with Wikia, but I don't care so much about that.)
This is certainly the right thing for Wales to do now, and for that I commend him. However, Wales really should have investigated whether Jordan's actions amounted to a breach of trust before appointing him to the Arbitration Committee. It was so widely known that Jordan had claimed to be a professor that surely Wales was aware of this. As Jordan's apparent supervisor at Wikia, one would presume that Wales was aware of the content of Jordan's work history and knew that he was, in fact, not a professor, and did not hold any advanced degrees. This alone should have caused Wales to at least wonder if he had misused his claim of academic credentials in some way. Surely Wales was aware that Jordan has misrepresented his credentials to the New Yorker; I cannot imagine that Wales failed to read that article.
In short, ignorance is not an excuse here, not when a reasonable person would have been suspicious. Wales, as a community manager himself, is obligated not to remain ignorant in the face of reasonable suspicion. He should have investigated; he apparently did not, and thus his actions led to this situation going from being merely embarrassing (the New Yorker thing would have broken eventually) to thoroughly damaging -- all because Wales appointed Jordan to the Arbitration Committee at a point where he (if acting prudently) would reasonably have known about Jordan's misconduct.
Lawyers have a catchphrase: "Trust, but verify". That is what Wales failed to do in this situation. His failure has harmed his own reputation, but even more so has harmed that of Wikipedia's. Hopefully, this will be a lesson for him, and for all Wikipedians.