Science is the ultimate long-tail of super-specialized interests with extremely small audiences, and Twitter is perfect for connecting those people with extremely esoteric interests.
There is a lot of crap, but science Twitter is also the only reason I'm on it. Sadly, my own biases against Twitter Kept me off it for 8+ years, but after I started finding the right people to follow, a whole new world opened up, and it is now a vital tool for me to navigate the literature and learn quickly which new tools are best.
That's really interesting, I've been avoiding Twitter for the same reason, but I can see how it'd help keep up with fast-moving niche fields. Maybe I'll give it a try, thanks!
Facebook seems like a much worse fit than even Twitter for discussion, but I would potentially check it out if somebody I trusted had found it useful.
Other than twitter, I'm not sure where else you can find that audience that is accessible to a layman.
Sometimes, reputation blocks science too, e.g. applied in reverse, the reputation-seeking prevents many false-hypothesis confirmations, because they're less likely to propel a career (or damage it).
EDIT: ...come to think of it, the scientific method is in itself reputation-agnostic.
EDIT2: ...imagine a world, where all science was public, open, but anonymized. No patents, no proprietary research. It's a dystopia for some, and possibly a utopia for others.