Since the last time on this thread I have taken the Stanford on-line course in Cosmology and in one of the lectures professor Susskind gave the reason for why the dark matter chunks do not collapse.
The first of 10 lectures is here:
Susskind Cosmology lectures
It is believed that the dark matter consists of a kind of elementary particles only interacting extremely weakly with other particles. The only significant interaction is by way of gravity.
This means that particles have no way to lose their potential energy so they will just obey the Newton gravity laws and orbit the common center of gravity forever.
In order for a particle to "sink" to the center it must get rid of the potential energy it has at the distance it starts out and there is no dissipation method available so it keeps the energy, which converts to velocity if it gets closer to the center in its orbit. That velocity in turn brings it back up the gravity potential well on the other leg of the orbit.
So these dark matter clouds are expected to have an extremely long life, much longer than the current age of the universe and thus never form black holes by themselves.
"Normal" matter on the other hand interacts with other particles plus the CMBR photons via the electromagnetic force and this causes them to gradually lose their potential energy so they truly sink towards the center of the gravity field they are immersed in.