If more than half the chaps are rated M, the entire fic should be rated yeah. Plus these days the featured rated M still gets on the homepage, so it shouldn't matter AS much. But its kinda lame when the featured fic has as one of the only 5 tags, yet its not rated...

I'm with Vividimole. I do not write many chaptered fics to begin with, but, say, there are four chapters and one of them should be rated M. In this case, I rate only the chapter and not the entire fic. If the entire story is violence and and whatnot, I rate the entire fic M. But eh, I guess one should just rate the work M even if only one chapter out of 23456 has or violence or anything else that needs a rating, come to think of it... After all, if part of the story isn't for the younger audience, it should probably not be for them at all? It makes little sense, actually, to rate a fic's chapters differently instead of the entire fic. Am I even making sense? I feel like I'm rambling as I'm thinking this through, pfft.

It depends. If there's something that should be rated in almost every chapter, then I would rate the whole story. But if there's that kind of content on one or two chapters in the story, then I would on rate these specific chapters only.