It may be the "wave of the future" for those who are already interested in such things, but I don't see it getting so pervasive as to mess things up for the rest of us. My idea of "social reading" is talking about books with a few people in the MR Challenge group on Goodreads, checking out reviewers there that I like, and that's about it.
If I come across a really spectacular passage worth sharing, I'll take the time to type it out. I've never really seen the appeal of sharing highlights beyond a few specific applications (like a study group, for example).
I haven't come across the sentiment that introverts are un-American, just that we're weird.
I'm okay with that.