It seems obvious to me that Actor-Network Theory (ANT) and Postphenomenology are complementary lenses for understanding social situations.
ANT gives us the network viewed “objectively” outside-in, and Postphenomenology helps us understand inside-out how the nodes interpret inputs from the network and translate them into outputs.
An ANT practitioner will be the first to tell you that ANT is just one way an actor (a theorist) can interpret and translate the network into a coherent explanatory account — but one that mostly blackboxes how that network is experienced at any one point. The ANT account is one of many multistable descriptions that can be given.
A Postphenomenologist brackets the network in order to understand how certain nodes in the network interpret other nodes before acting within the network, on the network, thereby changing it.
ANT and Postphenomenology are each the everted perspective of the other. Each methodically excludes what the other describes, through blackboxing or bracketing, respectively. A cultural anthropologist might say ANT attempts a rigorously etic view of the actor-network, and Postphenomenology is the emic view of the actor-nodes within it.
To make a chaos theory analogy, ANT gives us a Mandelbrot Set view of a region of the complex plane, and Postphenomenology gives us Julia Sets of selected points within the region.
OOO is a peculiar cross-breeding of the two that focuses precisely on the actor-nodes in the network that resist emic understanding, and then marvels at the fact that they must have some sort of emicity that neither we (nor any other object) can get at. They seem to me to be a mystical branch of Process philosophy, given to authoring fanciful philosophical midrash where both physical and social sciences fail.
To extend the chaos theory analogy, OOO enjoys boggling at how densely the points belonging to the Mandelbrot Set saturate the band of points along its psychedelically-enflamed perimeter, and at the impenetrable blankness of each and every one of them.