You might have seen this lament on New Year’s Day:
Second time that’s happened on a YouTube embed. I have no idea what the problem is. It may not make any difference, but I’ve put it back without changing the screen size, on the off-chance that there’s an issue with resizing.
Well, no, there wasn’t an issue with resizing. Apparently in WordPress 3.5, the combination of iframe tag and scheduled post results in iframe data being deleted from the post upon publication. WordPress has declared it a known bug. I expect it will be fixed by 3.5.1. Until then, I need to publish any YouTube or similar stuff in realtime, rather than schedule it.