One very salutary effect that blogs have on the publishing economy is that they bring work across my radar that print publishing, with its rather parsimonious gatekeeping, would never have brought out. I'm thinking particularly of graduate work; when the Google Books n-grams database came out, for instance, freakin' everybody had an opinion, but some of the smartest and most widely read assessments were by grad students, specifically Natalie Binder and Ben Schmidt. My Berkeley colleagues Lili Loofbourow and Aaron Bady likewise write widely appreciated, if less academically oriented, blogs. And Ladysquires, if you ever decide to depseudonymize, let me buy you a drink for writing the best lit pedagogy blog on the whole damn internet. There are economies of prestige on the internet and everywhere, but they're different ones than those that operate in academia, and for that reason, while the golden age of online scholarly communication may well lie ahead, blogs are already serving as a much-needed corrective to the manifold foibles of academic print publishing.
[UPDATE: I just came across Alex Reid's very smart post on the value of academic blogging. He wisely observes that it ought not become obligatory.]