ASCAP licenses the performance rights for music, collecting royalties for its songwriter members when their songs are played in certain contexts.

Those contexts now include a YouTube video embedded on your blog or website, assuming your site is not “purely” non-commercial and is deemed large enough by ASCAP.

If, and when, this does happen, you will see thousands of websites simply not embedding videos on their websites.  The free publicity for the artists will end and ASCAP won’t see a dime from anyone.  All ASCAP has done is continue to piss off regular people and drive them further from their products.