I'm not sure I see the link here (although it is definitely possible that I'm jsut missing something, I'm no physicist). I don't think Maxwell's demon needs perfect knowledge of the whole system -- it is just locally deciding to let through "fast" molecules and block "slow" ones.
I'm no physicist either, I just like to ask questions :)
How does the demon attain the knowledge of what is "fast" and "slow" without continuous observation (and thus interaction) with the particles. Velocity is just function of position over time, so the demon needs at least 2 samples to make the most basic approximation. Where is the entropy for doing that coming from? How does the interference of the measuring apparatus factor into the whole process - what if the sole act of measurement changes the state of the particle from "fast" to "slow" or vice versa? Do we need to measure twice? But what if the second measurement causes the transition it was meant to detect?