If they recognise it and the sample is long enough, yeah you do, I think.
There was a pretty big test case in the early 90s where Vanilla Ice (and Dr Dre, I expect) had to fight off being sued by Queen and David Bowie over the bassline on Ice Ice Baby. He ended up proving there was one extra note in his, meaning he didn't sample it, but re-recorded/re-wrote it.
It's a bit of a minefield, but as for sampling not being creative, I have to disagree. Crate digging for that perfect drum break, vocal or, well, anything is a genuine skill... for instance, Burials album contains samples from people like Christina Aguilera and Beyonce... but used in such a creative way that you'd probably never notice without being told. In a more traditional sense, I'd be hard pushed to say that a group like The Avalanches "cheated".
Or were you joking and I've just gobbled the bait? It strikes me that someone into Amen-based music would be ok with sampling....
