Hmm, lets bring in a big gun on this one, though not a musical big gun. T.S. Eliot (see I told you, for those who don't know him, he is probably the most influential peot of the 20th century), once wrote an essay about radition, and he said that true originality was taking things form other people's work previously, and creating your own thing. That is a pretty basic way of putting it, but if you look at his major poem, The Waste Land, you'll see what I mean, if you understand it at all (I know I don't). The poem uses qoutes and paraphrases and references to heaps of other literature, yet he clamimed that that was being original. That in fact, that is what originality is, not mistakenly trying to be different.
Anyway, I thought that was interesting.
From my point of view, I try to sound new, but I am happy admitting influences, and sometimes I love writing things that use other people's stuff and changing it. I have this piece written as a tribute to Neil Young, that uses a few lines from his music, as well as some other qoutes, and I deliberately attempted a Young style rock sound. Sure you wouldn't want to always do this sort of thing, but it is interesting.