Am continually impressed that certain Rhizome.org commenters can take whatever tech art development is currently happening and retro-fit a timeline for it,* proving that earlier generations had always been doing it.
One recently defined "social media" as extending backwards in time through '90s style homepages all the way to mail art in the 1950s.
This is not helpful. Like it or not, blogs didn't exist in the '90s (until the very tail end, and then only for a few people). Their arrival has changed the character of online art making and talk. How and how much is now being belatedly discussed.
When the next tech development (who knows, maybe dump.fm rooms?) supplants blogging and I invent bogus chronologies establishing my blog as an early version of it, you have my permission to slap me.
Afterthoughts (writing in progress--some of this I'm moving over to the Rhizome thread):
Social media art (the thing that we're defining) begins not with the advent of Facebook (Rhizome's "Blogging and the Arts" panel in '04 preceded that) but for sure the advent of blogging. The commenter was right that "networked culture" existed prior to Nicolas Bourriaud's "relational aesthetics" of 1998, which another writer used as a marker for the beginning of "social media art." But the commenter overshot by redefining "new media" as "social media" and tracing it all the way back to the Eisenhower era.
Blogging culture has partaken of (or accelerated) "relational" experiments such as live readings of twitter messages or YouTube playlists of MySpace intros but it didn't begin with awareness of Bourriaud (or Beuys, or Breton), it began with the invention of "last first" content management systems that allowed easy creation and updating of web pages, and faster networking between pages by means of comments, trackbacks, etc. The more relevant (or interesting) Bourriaud reference might be the "Post-production" essay and connections between blogging and DJ/remix culture; at least there is a shared origin in new kinds of technologies. I'd probably leave Mr. B out of the discussion altogether, since he apparently doesn't follow online stuff at all.
Update: We had a semi-coherent discussion of this on dump.fm. Some people want to fix the start date of "social media art" earlier than 2000 to incorporate chatrooms. Others want it to start with MySpace, so around 2003. People have started making cartoons about the discussion I was having with the commenter described above. Time to get off this topic, clearly.
*From dump.fm I learned a term for this, "retcon," for retroactive continuity. It's lingo from comic book writing, which fits for the kind of theory discussion we've been having.
Update, Feb 2011: Blogs occupy an important place in the chronology mainly if you value a record. Chat is/was generally not logged. Blog comments (in the era before comment spam) served as a form of chat, fairly close to real time depending on how heated the topic, but were also recorded and appended to the main post. The basic blog model has been refined by corporate social media (Facebook et al) by incorporating actual chat features and collectivizing content but I would argue the sea change was the arrival of the dynamic page where words didn't just disappear into the void. Am not arguing for blogging's significance (and certainly not it's continued relevance) just because it's my medium of choice, as was suggested by one of the Rhizome ad hominem arguers--am trying to be analytical here about these changes. It's ultimately probably not a point worth arguing because in the popular, media-fed imagination, social media is synonymous with Facebook and Twitter. Only nerds care about the underlying changes in technology and when they started.