my opinion in this: there are musicians who make music entirely out of, old, unknown samples and they create wonderful things which are totally original. (DJ Shadow)
I think the problem for me appears when the sample is taken of an entire melody or easily recognizable bit of a song that has already been created, like for example Big Time Rush's Windows Down ripped off of Blur's Song 2. (we could also use the Bittersweet Symphony example here but that song is awesome regardless)
Still sampling does not bother me at all at long as the song crafted on top of it is great.
An example of songs I like that sampled the same track would be:
Portishead's Glory Box
and
Tricky's Hell Is Around The Corner
They both sample Ike's Rap II in similar ways, though they create wonderful things on top of the song, I like both of them.
I personally think that modifying samples has created a new style of crafting music. A lot of genres have evolved from sampling such as Drum & Bass and Trip Hop. The Amen Break has been sampled countless times for every jungle and old skool D&B tracks such as the ones found in Goldie's Timeless. As a fan of those genres myself, I always find myself sampling bits of what I find and like, distorting them a bit to create the melody and ambience I desire. I sometimes create songs entirely out of samples and then throw in a pad or a drum machine or bass line to complement. After that, I hit the studio and replace any sample I can replace, be it guitar, drums, bass or keyboards. The finished song is a completely new, original song and the samples that remain are some that are left in the background and are usually reversed, distorted, filled with reverb and stuff so it's unrecognizable. That's my main method of creating songs so I am going to say YAY sampling. It's an awesome world to explore.