Have to admit that I'm kind of new to the food blog scene since I just started reading them regularly in 2008. Anyway, for what it's worth, here are my observations:
*Some of the famous food blogs seem to attract attention with their big, blown-up photographs. Upon closer examination, the bloggers don't know that much about food or how to cook well. They're just good at photography and maybe blog design.
*Some famous bloggers copy recipes word for word from other sites then say the recipes have been "adapted" from other sources. No. Lifting texts verbatim is not adaptation.
*Some really good cooks suck at writing and/or photography which is a shame. Their talents would have gotten more attention had they cared to take better pictures or invest in sprucing up their sites.
*Some famous, award-winning cookbooks authors are hopelessly bad at blogging. Makes you wonder how much work other people put into their award-winning books now that you see how bad they are when writing unaided.
*Some of the famous food blogs don't really have much to offer in terms of substance and the only reason for their fame which I can think of is that they started early when the competition for attention wasn't so fierce. These early bloggers seem kind of cliquish, too. It's almost like they've banded together to secure their positions at the top.
*Some food bloggers write very well, but don't seem to want to promote themselves. Sadly, they remain in obscurity and will perhaps remain there until food blogging dies off (will it?).
*Some travel/journalistic/documentary food blogs are devoid of substance and evidence of any real knowledge about different cultures and their cuisines; they just know how to take good pictures of Third World street kids in dirty clothes eating something exotic looking.
Not trying to be negative here. Just making some observations. Having observed these things, I'm glad I didn't take my girlfriend's suggestion that I start a food blog! You can find great food blogs that are underrated in other Chow threads where people recommend blogs you've never heard of. But so far I have yet to hear anyone talk about overrated blogs. In my opinion, without naming names, there are quite a few.