Impact over legacy has been with us since print media brought literacy and books into the marketplace. The
original class of professional writers , like Addison and Steele, Oliver Goldsmith, and others rather enjoyed the relative speed they could bring their views on issues and manners to the literate population; what would last among those pages seems an afterthought, as few of these writers seemed determined to write for the ages. That is likely what saved their pages from being consigned to a pile of dry, burning leaves, that they wrote well of their time rather than attempt future generations. Print and web values are not so opposed--clean copy, correct spelling, correct useage, a style one is in control of used to highlight sound insight and convey new information are what readers of either print or blogs prefer.
What is developing, I suspect, is that bloggers , at least those disposed to insist on standards for their preferred soapbox, are still translating those old concerns into their own jargon. One's own tongue is needed to make the fussy notion of "rules" a good fit. Also, the sheer surfeit of bloggers makes the situation for decent writing seem hopeless and makes one dread the suitable saw "quantity drives out quality".
I think the situation is less dire than that, concerning the state of English prose; it's been a fact that most of us inclined to write are not masters of the language we speak when it comes to writing it, and that the best of us, the most persistent word drunks in our midsts, soon enough become the ones who are the most read. Add to that these same folks are the ones likely to continue writing their blogs while most others will be abandoned and eventually deleted from their servers. Of course, we should remember that the technology is fluid and that blogging itself may soon join chat rooms as a quaint thing that is no longer a draw for most.