It's not the best analogy because there's already more junk out there than can fit through the limited bandwidth available to my brain, and yet I'm still (vaguely) functional.
So how do I avoid the junk now? Rough and ready trust metrics, I guess. Which of those will still work when the spam's 10x more human?
I think the recommendations of friends will still work, and we'll increasingly retreat to walled gardens where obvious spammers (of both the digital and human variety) can be booted out. I'm still on facebook, but I'm only interested in a few well-moderated groups. The main timeline is dead to me. Those moderators are my content curators for facebook content.