Symbolism, Imagery, Allegory
Throughout The Circle, Mae Holland experiences a number of disturbing episodes that frighten her. They often (but not always) occur when she's online, and they typically happen when Mae is overstimulated and stretched beyond her physical, psychological, and emotional means. Here's the first example, which happens as Mae falls down the rabbit hole of a never-ending comments thread:
Someone mentioned the usefulness of marijuana in alleviating glaucoma, and someone else mentioned it was helpful for those with MS, too, and then there was a frenetic exchange between three family members of MS patients, and Mae, feeling some darkness opening its wings within her, signed off. (1.13.4)
This experience of "darkness opening its wings" intensifies as Mae continues to adjust to life at the Circle. Here's how the novel's narrator describes the increasingly frequent "wave[s] of despair" that Mae has been feeling:
She'd been feeling this, this black rip, this loud tear, within her, a few times a week. It didn't usually last long, but when she closed her eyes she saw a tiny tear in what seemed to be black cloth, and through this tiny tear she heard the screams of millions of invisible souls. It was a very strange thing, she realized, and it wasn't anything she'd mentioned to anyone. She might have described it to Annie, but didn't want to worry her so soon into her time at the Circle. But what was this feeling? Who was screaming through the tear in the cloth? (1.30.14)
This image recurs again and again throughout The Circle, and although Mae never pins it down, it seems clear that the waves of despair are caused by her inability to process all of the information being dished out to her 24/7, not to mention her inability to engage in any meaningful way with the millions of people online who are becoming more and more connected to her every day.
On top of that, it's likely that on some level, Mae recognizes that there is something wrong with all of this, that what she and the Circle are doing is more morally ambiguous than anyone will admit. It's all just too much.
Mae's disturbing, Dante-esque visions suggest that human beings simply aren't capable of being all seeing and all knowing, whatever Eamon Bailey thinks. Mae Holland may be electronically connected to millions of people worldwide, but what good does that do her if she can't actually deal with all of that input?