GEOFF NUNBERG thinks he may have coined the word "logotariat", and he's probably right. He googled it when he wrote it and found no hits (and five years ago, the internet already had around 10 trillion words on it). He's not certain, though—making certain would take "more intense Zimmering than I'm capable of". He might have coined a second word there; "to Zimmer" would be to trace a word back to its earliest usages, antedating others' claims of the first recorded usage, as Ben Zimmer (of the New York Times) expertly does.
Back to "logotariat": Mr Nunberg's coinage shows not only how new words can come into the langauge, but how new suffixes do. "-tariat" is not, as far as I can tell, a traditional English suffix. It seems to have begun with two common words coming from French. Proletarius was the Latin term for a citizen of the lowest class in society. Prolétariat entered French to discuss the entire class of proletarii, using a French suffix -at to make a group or collective noun from prolétaire. English "secretariat," similarly, is a group or location of a group of secretaries, and came from French secrétariat as well.
If workers can show solidarity in a proletariat, and secretaries can feel grand at a secretariat, then someone thought it made sense to dub the self-important purveyors of commentary, as a class, "the commentariat". My OED is too old to have an entry for it, and MerriamWebster.com doesn't have either, and I don't have time to Zimmer further just now. The point is that people started seeing more and more words ending in -tariat about, and with "commentariat" they had a word that further implied a smug in-group feeling.
Remember that -tariat was still not a proper suffix itself; the -tariat words attach -at to words that end in -ary and their analogues: proletar(ius), secretary, commentary. It seems a fluke that all three of these also have a t, so that the group nouns all end in -tariat. (Commisariat is probably too rare to have broken this trend.) As a result, it seems, after a while speakers decided that there is in fact an English suffix, -tariat: a group of people who share a function or purpose, perhaps (like the commentariat) even smugly thinking they were more useful to society than they really are. Hence a spate of joyful new coinages, some more common than others: blogotariat, lawyertariat, punditariat, mediocritariat, idiotariat and so on, all with the same connotation. Some of these words usefully already end with -t and so are crying to be made into -tariats (punditariat, idiotariat). Blogotariat requires an intervening -o- to make the rhythm right for most folks; blogtariat is far less common out there. But notice that nobody seems to have thought "blogariat" was the right word. -tariat is the clear winner.
Executive summary: take the Latin ending -arius, make it the French -aire, make the collective noun -ariat, import it into English, generalise from the fact that most common words happen to end in -tariat, add "smugness" to the connotation (generalising from "commentariat"), and presto. New suffix. I, for one, welcome our new logotariat overlords.
(Some of this, admittedly, is speculative, especially what I've posited about how the -t crept in there. If anyone has the resources to Zimmer more ably than I have, let us know what you find in the comments.)