I'm trying to post a video from Blip.tv. And here's your page to do that: http://en.support.wordpress.com/videos/bliptv/
So, this is what I copied from Blip.tv and pasted to the HTML editor:
'<iframe src="http://blip.tv/play/gYY47ON7Ag.html?p=1" width="550" height="442" frameborder="0" allowfullscreen></iframe><embed type="application/x-shockwave-flash" src="http://a.blip.tv/api.swf#gYY47ON7Ag" style="display:none"></embed>'
And upon publishing it, the code changed to this:
'[blip.tv http://blip.tv/play/gYY47ON7Ag?p=1 width="550" height="442"]'
So it should work. Only thing is it didn't. There's nothing on it. It's published privately. I'm not sure if you can see it, but here's the page address: http://wp.me/p14KQW-5R (I'd give you a screen shot, but here's no option to add a picture.)
Blog url: http://mathloving.wordpress.com/