When Woody Guthrie was singing hillbilly songs on a little Los Angeles radio station in the late 1930s he used to mail out a small mimeographed songbook to listeners who wanted the words to his songs. On the bottom of one page appeared the following: This song is Copyrighted in U.S., under Seal of Copyright #154085, for a period of 28 years, and anybody caught singin' it without our permission, will be mighty good friends of our'n, cause we don't give a dern. Publish it. Write it. Sing it. Swing to it. Yodel it. We wrote it, that's all we wanted to do - Pete Seeger, on Woody, June 67
I think youtube only wants to support embedding based on the URL construct defined in the "Share" tab, so grab the URL from there, THEN remove the "s" and presto... embedded video.
If we could get a Mac enabled weenie to reproduce the error and fix, that would be great. Here's a little screenshot splaining where to grab the correct (Share tab) and incorrect (Address bar) URLs from.