This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
I believe that *usually* the behavior will be to not play until the user explicitly clicks "play" (instead of starting play as soon as the page starts loading).
But that's completely up to your player (which, of course, is invoked by your browser).
The whole "<object>" vs "<embed>" issue (to say nothing of "autoplay" vs "autostart") is completely non-standard, so it's really anybody's guess what's ACTUALLY going to happen for a given user on a given browser ;-)