Legal or illegal doesn't necessarily equate right or wrong. (In fact, I'd go as far to say that most of the time it doesn't)
Anywho, as for sampling.. if it is done in a manner that puts a new spin on a song (remixing) or is used to create something entirely new (slicing beats, hip hop stuff, etc).
Unfortunately, the disease that is copyright law doesn't agree with that, and thus legality varies depending on use and location.
So maybe the next thought should be:
Copyright Laws: Right or Wrong?
I'd definitely argue favorably for copyright when it comes to attributing the original artist of a work, invention, production... whatever. If you make something, you should be properly credited and compensated for it.
Unfortunately, copyright laws nowadays have expanded to the point where they can heavily suppress creative thought and forward movement in society.