I saw the webcast on KROQ's website. Needless to say, my opinion of them is pretty lame because i've never actually seen them in perosn, but this is what i got from the webcast:
Franz Ferdinand was on before The Killers, and it just seemed as if the crowd was more into it-more background noise. Now, when The Killers played their first few songs, which were more of the upbeat variety, i heard much of the same cheering from the crowd. But when they broke into their slower material (which i think is pretty blech btw), I didn't hear the same amount of crowd support.
From what i heard, they sounded pretty good live, but maybe some of their songs just aren't ready for large venues?