Another excerpt from Dr. Bill's link for non-clickers (though I recommend reading the full text, it's a stimlating and worthwhile read):
If the question that scientists pose for themselves is simply too difficult, they are limited to pure conjecture. For example, in the Middle Ages, how Earth was formed was a question scientists could only guess about. Science can only make progress by taking small steps. Today, if we were able to answer the limited question "How did life on Earth begin?" it would be a rather large small step, wouldn't it? If we figure out that one, we probably deserve a vacation before we tackle the next problem.
Yet many scientists continue to assert that the question is how life began in the first place. They say that knowing life on Earth comes from space would be of only minor interest because it sheds no light on the question. This position is detrimental to science; in fact, it is dumbfounding.
If one had to compose the question for all of science, it should be something like "What's going on?" Isn't that what we really want to know? With that attitude, it is fruitful to ask more and more precise questions. If we continue to insist that the question about life is "How did life begin in the first place?" we establish ground rules that may keep us from ever finding out what's going on.
Even if we never find out how life begins in the first place, it makes a lot of difference where life on Earth comes from. If life comes from space, evolution could work completely differently from the way we were taught in school. New genes could come from space throughout life's history, even today. These arrivals could be the source of evolution's raw material—new genetic programs for evolution to sift through, as discussed in the sections under "How Does Life Evolve?" This makes a pretty big difference in our understanding of what's going on.
Under the old theory we are completely isolated from the greater universe, including other life in it, if there is any. If life comes from space, life is probably abundant in the universe and we on Earth are related to it. This change has profound philosophical and psychological consequences. This makes a really big difference, as we will discuss.
