Occasionally, electronica djs will mix in a soundclip to create something more than blips and beeps backed by beats. They're typically added through production, not live on the tables (even most scratch masters don't do this live unless they're battling). If it's not something being done on the fly, we can be critical of production quality.
Here's an example from DJ AtomX with clips about the Goldstone Observatory that's done well:
and here's one that DJ Jon Carpenter spun that's not so good:
The clips should blend seamlessly (the second set really don't), and they should accent the song, not be the song. Otherwise we'd just put a techno track behind the state of the union and Americans might actually know what the fuck is going on.