It’s probably impossible to answer this question. It’s a bit like asking, “what makes a good book?”
Blogs are so many things to so many people – they are forms of journalism, pedagogical tools for university courses, personal diaries, social hangout spaces, places for writing fan fiction, locations for software to be released and discussed… The list is as long as the uses to which blogs have been put, which is to say, more diverse than I can mention.
Although “early” blog theories (that is, those from about 5 years ago!) emphasised the keeping of journals and diaries as the main function of blogs (Viviane Serfaty’s book is a good example of this notion), the explosion of different uses for blogs has led some more recent definitions to reduce what-blogging-is to bare technological terms – that is, blogging is a medium. This way of defining blogs reduces them to something like this: “Blogs are an online publishing tool; blogs consist of a series of individual “entries”; these entries are usually displayed in reverse chronological order.” (Wikipedia’s definition is along these lines.)
As Jill Walker Rettberg explains in her great little book called, simply, Blogging, within this bare-bones techno-definition of blogging as a medium, various genres can be sifted out: political blogging, filter blogging, diary-style blogging, and so on. Each of these genres (and its attendant sub and sub-sub genres) comes with its own set of conventions, and within the genre, those conventions make sense – they can be used to determine a “good” from a “bad” blog.
In general, though, Walker Rettberg presents three basic criteria which define – not what a blog is, but how it is (p.21). Those criteria are “frequency, brevity, and personality” (she borrows these terms from Evan Williams, the fella who invented Blogger). She then goes on to explain that the first two of these criteria (frequency and brevity) are formal qualities associated with blogs. The third criteria, however, points to a further feature of blogs which is very important, and pertinant, I think, to the question of what makes a good blog – personality. Blogs, she writes are “generally written in the first person”. They are subjective. They are social.
How does this help us think about what makes a good blog? Well, if Rettberg Walker’s last point is true (and I believe it is, wholeheartedly) then the question becomes something like – “what makes a good friend?”
My friends are people that I trust. I trust them, not because they come with some kind of accreditation or references (as I would require if hiring someone for a job). I trust them because of some action they have performed, in relation to me, which makes me believe they are trustworthy.
Perhaps they helped me solve a problem I had. Maybe they told a story about themselves which made me think differently about my own relationship to the world. Or they made me laugh. Or they listened to me when I had something to get off my chest. Whatever the case, hanging out with them was a rewarding experience, regularly enough, for me to say, “I like him/her”. The effort expended in passing time with them was worth it. So I kept coming back, and a relationship between us – friendship – was formed.
And it’s the same for “good” blogs, I would say.