Natural vs. Synthetic is a touchy subject...which has raised lots of argument. If you want to read about the flame...take a look at Luca Turin's old blog, or Perfume of Life's forum.
All I will say, is that synthetics are a very important part of perfumery. Guerlain's Jicky claims to be the first to incorporate synthetics into a perfume, although I believe Houbigant released something prior to it containing coumarin. Anyway, yes, some can pick out synthetic notes, and allegedly many "natural" perfumes in fact aren't really all that natural.