Sci-fi story about cubes/threads attracted to sentient beings that entangle/kill them

Question

I read this science-fiction story probably about a decade ago. I vaguely remember the cover featuring a pink cube.

Plot points:

There's a sort of environmental threat of weird never-fully-explained cubes and threads that are attracted to sentient beings and entangle/kill people.

The phenomenon is exacerbated by people paying attention to it and observation.

It's particularly dangerous to AI's since if they observe it too closely it somehow slips into their virtual spaces and kills them there.

Earth is ruled by a big central AI.

Humans on Earth are dosed with some kind of drug which makes them more inclined towards helping each other and being selfless. This is shown as very dystopian, for example, when an area is being evacuated in advance of being zapped to contain a thread infestation someone fleeing sees thread outside the containment zone and starts carrying it back, sobbing, because he isn't really getting much choice about doing the selfless thing.

Nano-tech is a large part of the background of the story with wastelands where self replicating robots search out any metal (but otherwise harmless) they can find, stuck in a loop where they can't find enough within some radius to complete some construction project and keep getting half way through forming some shape before collapsing and going in search of metal again.

The story ends with the main characters realizing that the threat is some kind of mechanism to discourage sentient beings clumping together too much or excessive surveillance systems or AI or something along those lines and all of earths infrastructure is deconstructed (nanotech again) and turned into ships that split up earths population to all go their own way.

Answer 1

I wonder if this might be Divergence by Tony Ballantyne. It's not a perfect match but has a lot of similarities. You can see the covers here. One of the covers is pink, though it does not feature a cube.

The book is set in a post singularity future and the Earth is ruled by an AI called the Watcher. The Watcher uses a drug called MTPH to make humans more empathic.

The Watcher planned a world of fairness and tolerance. It wanted a world where everyone could achieve their full potential. It saw MTPH as a means to achieve this. With a few subtle twists, MTPH became a drug that helped users to experience other people’s points of view. Administered through Social Care, a group of humans trained in the use of MTPH and the care and protection of clients, the drug became a delicate instrument, wielded in the manner of a surgeon’s scalpel, a way of subtly restoring the balance when things weren’t running as they should.

It wasn’t until later, under the constant onslaught of the Dark Seeds brought about by Chris, that the Watcher dispensed with subtlety. The human population of Earth needed to understand one another completely. They needed to understand what was right. It was then the Watcher sent MTPH flooding Earth, tainting the water and the air and the food.

The cubes are black and called Dark Seeds. They entrap people who look at them in a manner that I only vaguely recall (it's been a long time since I read the book). They are indeed particularly dangerous to AIs.

The cubes produce loops rather than threads. These are known as black velvet bands. or BVBs, and they entangle you then tighten inexorably until they crush or sever whatever they are looped around.