First, the original work was created by someone else. Rights can be purchased, and permission can be given, but the fact remains that the sampling artist ends up getting the credit for writing it, since invariably, the sampled passage is the most distinguishing part of the final song.
Second, I believe that the more reliance that is put on sampling, the less true "songwriting" is actually going on. If we take this concept to the extreme, we would eventually get to the point where every new "song" is simply a DJ-like "mix" of previously-released material. At this point, no truly new music would be being created, and wouldn't that be a shame?
Lastly, the ability to sample entire musical passages lessens the desire for young people to take up an instrument, since the process of songwriting can new be streamlined. Yes, it's great that more people are now able to enjoy their involvement in music, but I've most certainly seen a decline in young people's desire to emulate their favorite guitar player or drummer. Instead, a desire to emulate their favorite "DJ" who can neither write his own music, nor play an instrument.
In conclusion, I see sampling as an effective music-making tool if used properly. If used abused, I see a downward spiral where no truly new music is ever created and every "new" song is a homologation of previous work.
Houses cannot be built without foundations, but in the distance, I'm seeing a city of skyscrapers being built on swampland.
Flame away...
