Deportation is one thing; banned from returning is something else. I'm against holding someone responsible for their path indefinitely. I'm of the school of thought that people can change, even the worst of society, and with that I think that banning someone from returning to the U.S. is completely unnecessary. Perhaps banning them from returning for five years, or even a decade is acceptable, but not indefinitely.
Everyone has their own reasons for wanting to come to America. If they come, and are deported back to their homeland, they will have realized one of two things: a.) that America is not all it's hyped up to be, and therefore don't see any real need to return, or b.) that America is what they hoped it would be, and that they shouldn't have taken it for granted.
That said, I don't think people should be deported unless they've committed very, very serious crimes.