Being seen to be human flesh in one case doesn't mean all instances are human flesh. Otherwise there wouldn't be a seperate item called http://fallout.wikia.com/wiki/Human_flesh_(Fallout:_New_Vegas) with seperate stats from http://fallout.wikia.com/wiki/Strange_meat_(Fallout:_New_Vegas) Despite what the wiki claims.
I'd say that human flesh is used when you KNOW something is actual human flesh, while strange meat is used when they want to deny that it's human flesh, as in "No, we're totally not cannibals, definitinately not cannibals at all!" type denial. In any case, if it wasn't mean to be the same thing as the strange meat found in Fallout 3, which was implied to be human flesh, I doubt they'd call it by the same name.
Yes, I'd say that strange meat was human flesh in Fallout 3 and still is in New Vegas, and even if it's not human flesh, I wouldn't want to eat it. Would you want to eat something called "strange meat"? I mean, they won't even tell us what kind of meat it is! At least you know what you're eating when you eat radroach meat.
As for the abundance of it in the game, I'd guess it's just a mistake on Obsidian's part, although some instances where it can be found in places inhabited by known cannibals are likely intentional.
Didn't find it so unusual even if it is a bit more common in NV, just seems like in the wastes it would be somewhat common practice to use anything you could to survive.
I don't know, considering how most people in the game treat cannibals, it would seem pretty hypocritical if eating human flesh was actually common place, even if it was for survival. Granted, maybe just eating people who are already dead would be treated differently from actually killing people for their meat, which seems to be what most cannibals do, but considering that cannibalism generally seems to be treated as much worth than just plain murder for other reasons, I doubt people would consider it okay just because they're already dead.
Besides, in terms of food, it would seem to me that finding normal edibal food would be much easier in New Vegas' environment than in the Capital Wasteland, since there's actually signs of agriculture in the Mojave, so if anything, I'd think cannibalism would be much less common in the Mojave than in the Capital Wasteland.