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.