I guess that the most shocking bit about the whole thing is my epiphany: "I don't care."
Don't get me wrong, I do believe that it is important to have a good grasp of English. Anyone who writes had better know something. If you don't, well, you better be willing to put in the time to learn it!
That said, I think there are a few behavioral shifts we need to recognize before discussing the relevance of grammar to social networking sites:
1) Spoken language is not the same as written language.
2) Technology is affecting communication.
3) In spoken language, grammar and vocubulary usuage is dependent on context.
4) Texting and social networking are equivalent to conversing, sharing experience (like playing sharades at a party consisting of acquiantances)or even waving at
someone when walking down the street (poking, throwing sheep, etc.)
If social networking sites and texting are analogous to these casual forms of communication, the only part of it that makes standard grammar important is the fact that it is textually based. Writing has traditionally been the most formal of all forms communicating in English. The advent of writing has actually hindered natural language change, stalled it to such a degree that the alterations have been minimal in the past 500 years. (Yes, Shakespeare IS Early-Modern English.) All sources for proper grammar and vocabulary come from written works. We use dictionaries, thesarus, novels, and non-fiction texts to inform us of any topic we need. As we do so, we perpetuate standard English.
Bravo and Brava! Job well done, Reader!
But suddenly, context for written communication is broadening. As writing starting to take on the same contexts as spoken language, it makes sense that written grammar will become as context-dependent as spoken language. The lesson should be when to use it in which way. Standard English, in written form does not convey emotion the way that a voice would. In order to meet this need in casual textual conversing, the language changes. Grammar, which conveys its own loaded meanings, is changed to fit the needs of the society utilizing it.
Will this change formal documents? Of that I'm not certain. I certainly hope the alteration won't be extreme, but there is bound to be some reverberation. But then, language is the verbal (and textual) expression of culture, the communication of ideas and so forth. As those things change, and culture changes, so too does language.
From my standpoint, that is inevitable and nothing to balk at. I'm excited. it will be interesting to see what affects this has on formal writing...