As a DJ, I love taking requests and try to accomodate them. But when I've spent 20+ hours on a setlist for the party, it can be a bummer to get a request like "Uhh, something by Bruce Springsteen?" Especially when I put on said track, but it wasn't the song they were thinking of, and the people requesting it don't even bother to dance. Literally bad requests can kill a party.
The worst time was when someone threatened by life for a request for the Cupid Shuffle when I had just played it. I would rather have had the $10 bill!