The question inspired by an upcoming colloquim at UCB.
A naive interpretation of quark asymptotic freedom seems to imply that at high enough energies they should be weakly interacting. On the other hand, the quark-gluon plasma accessible experimentally via heavy ion collisions is claimed to be close to an ideal liquid. There is also a lot of excitement about this because of AdS/CFT correspondence (see this and related questions at Physics.SE).
Shouldn't the quark-gluon matter phase diagram be close to an ideal gas at least in some low-density & high-temperature region? In other words, is quasi-independent quark gas picture of QCD ever valid? And is there a simple reason why?