From a semantics standpoint, there is a world of difference between the two terms. Reason, on the one hand, is a verified (and verifiable) fact that logically justifies either a premise or conclusion. From its definition, one gets the sense that reason involves an evidentiary inquest. Faith, on the other hand, is something entirely different. By its definition, faith implies a trust, belief, or acceptance without evidence or investigation. From this perspective, faith and reason appear to be strict antonyms, rather than compatible terms.
I am troubled when I hear people try to force together the terms, as if they were jamming a square peg into a round hole. To argue, as some have, that faith is what happens when you exhaust reason is insulting to the very foundations of academia. In academic inquiries, the conclusions we draw must always be based upon the credible evidence that we have at our disposal. Any academic worth his or her salt would find it reprehensible to say, when the evidence and logic does not support the hypothesis, that you can simply continue believe something to be true. As far as I'm concerned, this sort of faith is not a virtue.
I have heard others remark that faith and reason are compatible because they can be interchanged to answer life's questions. The specific quote, I believe, was that faith is important because "reason and science can't explain everything." There are too many things wrong with this statement to catalogue in this post; suffice it to say that such utterances make the hair on my neck stand on end. It is a non sequitur (that is: it does not follow) that if science or reason doesn't yet have the answer to a question that faith should automatically become the default alternative. Why would faith be an appropriate substitute for reason? Faith has a terrible track record when it comes to getting things right (see: the shape of the Earth, the nature of the solar system, the cause of disease and natural disasters etc, etc., etc!) I would have thought that faith lost its right to sit beside reason, as a method of observation, a long time ago.
I cannot be sure of the motivation behind such attempts to force together faith and reason. I would suspect that it is done in an effort to bolster the credibility of faith, specifically religious faith, so that faith can give the appearance of having a logical or evidentiary basis. In reality, by arguing for interconnectivity between faith and reason, one establishes a false compatibility that subverts the natural tension between the terms. Reason relies solely on logic and the evidence to form a conclusion; faith implies the willingness to maintain a belief, in the face of contrary (or lacking) evidence and logic.
Some might find it sophomoric to harp incessantly on the definition of the terms -- everyone cringes at the freshman paper that begins: "The Oxford English Dictionary defines the term _____ as ____." However, I would argue that it is important, in this case, to understand what these terms mean. Failing to do so enhances the possibility that one will misunderstand the nature of the question and wrongly (in my opinion) argue for compatibility between faith and reason. In the end, faith and reason are very different things. They are not, in my estimation, the least bit compatible.