Guys, have you ever heard about tabbed browsing?? When I parse a page I might open all it's links in the background into new tabs. Middle Mouse button – click, click, click, click… Like this it goes real fast that I have two dozen of tabs open….
Now imagine that at least two of those are playing audio … plus my winamp streaming in cool funky music. What a chaos!! What do I do? It's hard to find those and it cost time thus I simply close one tab after the other until audio is gone!!! And probably I won't come back to your site.
So don't play audio oder video until explicitly requested by the user! See the embedded YouTube videos? You have to click on them to confirm that you want to load them and see them now!
Moreover offer buttons for stopping playback and muting audio.