According to abundant forms of colocationism, where I sit, there sit an infinity of other individuals. One of these individuals is a human-shaped mound of flesh and blood. Another is a philosopher. Yet another is something one might call a "rigid human figure" (which I will explain below). These individuals are all related to me in having the same matter. Their distinctness can be seen from the fact that they have different persistence conditions. Thus, the mound of flesh and blood can survive my death, while the philosopher came into existence significantly after I did. The rigid human figure does not survive changes in the orientation of bodily parts. According to sparser forms of colocationism, we may have a more limited number of individuals present here—only the objects that fulfill some philosophically explanatory role will be posited. Thus, the sparse colocationist will probably admit the human-shaped mound of flesh and blood, but probably will not admit the philosopher or the rigid human figure.
Colocationism, whether abundant or sparse, multiplies individuals where there is a multiplicity of what one might with significant propriety call "natures". This creates a prima facie problem for the Incarnation. For if such things as being a human and being a mound of flesh and blood count as individual-defining natures, surely so will being a human and being divine. But then the colocationism seems to imply that where Jesus is, there are two distinct individuals, one of whom is human and the other of whom is divine. This is Nestorianism. (We are used to formulations of Nestorianism that use the word "person" instead of "individual". But we could also have used "individual" as our gloss on "hupostasis"—the Greek does not have the personal implications of the Latin. In any case, both of the individuals will be persons, so there will be two persons.)
This is a prima facie problem for colocationism (I assume, of course, that the orthodox doctrine of the Incarnation is true). Colocationism's multiplication of individuals seems to multiply Jesus into at least two individuals. One attempted solution to the problem might be to say that there is only one nature there, maybe "Godhumanhood". But that, of course, threatens monophysitism, unless one can argue that the sense of "nature" here is sufficiently different from that of the Council of Chalcedon. Maybe if one makes the right distinctions, one can get out of this problem. But it's going to be hard (every account of the Incarnation is hard, but here there seems to be an additional difficulty).
Abundant colocationism has a further problem. There will be an infinitude of individuals where Jesus is. A human, a teacher, a carpenter, the King of Israel, the Messiah, etc. Even if somehow we manage to collapse the human and the divine individuals into one—if not, we get Nestorianism—what do we say about all these other individuals? Are they, for instance, individuals worthy of our worship? Presumably not all—for only three individuals in existence are worthy of worship (in the sense of latria): the Father, the Son and the Holy Spirit. The carpenter, the teacher, the King of Israel, the Messiah and the mound of flesh and blood all share the matter of the (incarnate) Son, but are distinct from the Son, and a fortiori from the Father and the Holy Spirit. But there is something more than a little odd about saying that the Messiah is not to be worshiped. Moreover, while this particular multiplication of individuals may not violate the letter of the Council of Ephesus, it seems to be very much in the Nestorian spirit. If it was bad to have two individuals, having an infinitude surely is also problematic. We want to be able to say that the individual that Jesus' disciples were taught by was the Son of God. But when Jesus' disciples were taught by the teacher (whom else do we attribute teaching to in the primary sense but the teacher?), then it seems they were taught by someone other than the Son of God on the colocationist view.
The sparse colocationist has less trouble, perhaps. She might only have the flesh and blood and the human being to deal with. To avoid literal Nestorianism, she will say that the human being is the same individual as the Logos. The mound of flesh and blood will still be problematic, though, in light of the fact that we are told by Scripture that the Logos became flesh. We do not want to leave the flesh and blood too far outside the bounds of the Incarnation.