Just now I thought I'd try Pandora out. Went over to their website expecting to have to sign up or download something. Nope, they let me pick an artist and just started pumping the tunes out. Awesome! After a few songs I start getting interested in one of them, so I click a link to show more info about the artist. Music cuts out abruptly and I'm put in front of a sign-up page. I spent ten seconds trying to figure out how to get the music back on before signing up. Discovered I can't do this, so I closed the browser tab and fired up iTunes.
The experience was so annoying I actually had to write a comment about it.