Both of those threads ended with the assumption that YouTube’s end of the process was the problem. However, I’m the network administrator on a 3.1 Network of blogs but when I post a link to a video it works and when the administrator of a specific blog in the network does so, it does not.
We even tried to revise a post with my account and then have the admin copy/paste the working post and embed from my revision into a new post connected to her account and it still only posted the link. Is there some capability different between the network administrator and a blog administrator that could mess up the oEmbed features?
I’m leaning toward installing a plugin for the network to provide this functionality, but (like the one linked to from both of the threads above) but would prefer to understand the problem fully before I work around it if at all possible.