Corn, generally speaking, can be eaten raw and is thus as paleo as anything else (see caveat below).
Modern corn? Well, it's often GMO, as Kurite pointed out. Go for the organic and the local and you'll be better off.
You need to be certain of the type of corn under discussion, however. The corn of which I speak is "sweet corn", which is harvested in an "un-ripe" stage and can thus be eaten raw (as a vegetable). If left to mature, it turns hard and must be cooked like any other grain...thus rendering it distinctly neolithic.