I've never done that. Dialogue clips sure but I've never been interested in sampling a popular song.
Yeah, I mean basically anything that's copyrighted. Sampling songs is trickier.
Okay, for example breakbeats. That's a song that you don't own at all. But it's like a nod to another artist... You're not pretending that you made it. I don't know, I guess even that is a little sketchy, because those drummers who made those breaks do deserve money.