I have been reading David Denby's book, Snark. I have some problems with that book, but they are essentially the same ones that the reviewers have talked about, viz., that Denby's book is ultimately dissatisfying because it adopts a partisan view of snark.
It seems odd to me that an obviously smart person like Denby - or his editor - would not have noted immediately that when taken in total, snark in his view seems to be correlated pretty much with the right, and not the left. I suppose it might turn out that this is the fact of the matter, but it seems unlikely, and anyway is not demonstrated on Denby's evidence. What is demonstrated on Denby's evidence is that he regards snark in an ad hoc way - if he likes it, it is clever, well-aimed satire, irony, and parody, and if he doesn't, it is snark.
The fundamental problem in defining snark - and in saying that it is bad for the blogosphere - is that no one, least of all me, really wants all high-minded argument on the web, all the time. The problem is how to distinguish, on anything other than the least satisfying ad hoc, subjective, personal or - worse - political criteria satire, irony, parody from ... snark. Whatever exactly it is. We want A Modest Proposal; we don't want ... well, what? One general principle is to be reasonably understanding that humor is both subjective and risky, so as readers one should be reasonably forgiving even of efforts one thinks have flopped. Not everything is as pitch-perfect as the Onion, and even there lots of what I find funny, my mother would not have.
But beyond humor that misses, with some audiences or with all, what characterizes snark? Two things, I think. One is that it is an appeal to emotion - it is a statement with a particular affect, and the affect is an appeal to an attitude in which both writer and reader participate, but they participate in an exclusionary way. This is what makes it a branch of irony. Instead of arguing to everyone on the basis of shared reason so that, at least in principle, everyone could be included in the shared sentiment, snark depends upon exclusion. It is a refusal to offer a public argument, with the possibility of reasoned inclusion, and instead depends upon prior shared views that merely exclude because snark does not make an attempt to persuade. It is 'affectively exclusionary' in the language of moral psychology.
(Note that the greatest satire and irony appears to be exclusionary in this way - but ultimately is not. A Modest Proposal is the bitterest satire, and yet it ultimately is inclusionary, because underlying it is an appeal to a universal sentiment in which all can participate. It is not a reasoned argument, and is not an invitation to inclusion on that basis. It is, rather than argument, an invitation to see the universal moral impulse beneath the satire, and to demonstrate it by a reductio ad absurdum - an invitation to apperceive the universal value. It is a little like the Christian concept of conversion through the bearing of testimony. Despite the surface irony, in other words, truly great satire is actually an invitation to see and join the community of believers, not exclusion from it.)
Two, because snark depends upon a prior shared commitment, it is a form of question-begging argument. Not precisely a form of argument, because it is about affect, not reason. So, more precisely, snark is the affective cognate of a question-begging argument, in which the sentiment of the conclusion assumes the sentiment of the premise. It assumes that one already shares the attitudes necessary to ... share the attitudes.