One way of looking at the map is to split states according to what sorts of candidates they can vote for, at least since 1988. Who runs matters greatly:
Red -- Vote indiscriminately for Democrats, at least since 1992. Only a very strong conservative Republican, one with a nationwide appeal, has a chance to win any of these states. This is a very strict standard; I exclude Wisconsin because it nearly went to Dubya in 2004.
Could it be that conservative Republicans can no longer win these states in statewide elections?
Green -- These states can vote for a southern, moderate, rural Democratic populist like LBJ, Carter (1976), or Clinton, but probably not for a northern or western liberal. Does the southern moderate rural Democratic politician really exist? None will be available until at least 2016. Obama and Kerry got clobbered in these states. Obama wins any of these states only in an electoral blowout
Yellow -- Genuine swing states that have vulnerabilities for Democrats or Republicans who miss something. They have all voted at least once for a Democratic candidate for President since 1988 (which may include Obama); even if they didn't vote for Obama they were reasonably close. I include Arizona, which Obama would probably have won except that the Republican nominee was from there. This now includes Indiana and North Carolina, both of which voted -- barely -- for Obama and for the first time for any Democratic nominee for President since 1964 or 1976. Except in an electoral blowout, no candidate can ever win all of these states.
Blue -- These states seem to indiscriminately vote Republican. The most likely ones among these to flip to Obama are the Dakotas.
I wouldn't put Georgia into the same category as a state like Missouri; likewise with Indiana. Indiana, especially, is a fluke more than anything else. It won't go Democratic at a 50/50 election, which should be the standard for judging swing states.