Update: Hmmmmm, apparently not without totally screwing up the site. Let me go get a plug in.
Update Update: Testing again:
Okay, this is interesting. Because I have AdBlock Plus on my Firefox install, anytime I edit this, it inserts the AdBlock plus code into my entry, which screws the coding. Fascinating.
Solution: Edit entries with embedded video in IE. I know IE was good for something!
Incidentally, I didn’t add a plug-in; I just clicked the checkbox that allows WordPress to correct invalid XHTML code. Just in case you were wondering.