Pardon me, I'm not too SAVVY (hah! pun intended..you'll see why in a sec) in the film music world, but is it common for major films to use samples?
Have a listen to this clip from Pirates of the Caribbean (now you get the pun, if you've seen the movie):
The strings in the very beginning don't sound very realistic to me. And the brass sounds a bit thin. Actually, I had the opportunity to hear what Zimmer's custom horn lib sounds like (don't ask), and this is kind of what it sounded like. So is this samples? Or just a really bad mix?