In this artical that precedes some papers to be published in Icarus they discuss formation of planets and moons.

One thing puzzles me and maybe you guys can 'splain it to me. The author says there will be a tendency for a growing moon to move closer to its primary as it sweeps through the existing gas cloud. He goes to some length to explain how all moons don't end up accreting with their primary. Now my problem with this is that I thought that a moon's (or a planet's) orbit resulted from the net orbits (vectors) of all of the things that went into building it. If you are talking about a gas cloud that is busy building a gas giant, and there are leftovers to build moons with, then the moons are being build of gasses that are already in orbit (not at rest - whatever that would mean). Wouldn't moving through this gas (capturing some) that was already moving in approximately the same orbit as the moon have only a minor effect on the moon's orbit?