Are Maps mashups patentable?

Someone asked me today whether they could file a patent application concerning their Google Maps mashup.  Not being a patent lawyer, I haven't the foggiest, but it's an interesting question.  I don't see anything in the API Terms that would specifically preclude patenting a maps app.  (Commercial use of the API seems to be ok, though a bit of confusion about this is apparent when you search on the issue:  "The Service may be used only for services that are generally accessible to consumers without charge."  See also Jeremy Zawodny, Yahoo! Maps API, now for commercial use too.)

I assume that under the right circumstances the answer to my question is probably yes, but I'd enjoy hearing the thoughts of those more in the know.  Regardless, I can think of no better subject matter for inclusion in WikiPatents, "a public community that reviews US patents and pending patent applications. The public can add prior art references for a given patent, vote on the relevancy of both original and user-added references, and make comments about how the prior art is related to a patent. Users may also vote on various market and technical merits of patents and patent applications" — something I discussed briefly with Dan Farber in his podcast this week.

[Updated September 3, 2006 @ 8:53 am:]  The related, perhaps controlling, question is the extent to which incorporation of another's patented work (even where, as here, it's done with permission) might preclude the patentability of the new work due to issues with prior art, novelty, originality, etc.  In the comments, Dave Leigh also hits on why this question struck me as intriguing to begin with, and why I first took a look at the terms of the Google Maps API.  It seems like the ability to patent something based on an open API would be contrary to at least some of the motivations behind the API's liberal terms of use, so I wondered if this was something Google (or others providing APIs?) has tried to limit explicitly and contractually.