Over in another forum I've got myself in trouble by suggesting that theoreticians haven't paid enough attention to this question. George Jones has kindly pointed out that the question seems to have been answered along the lines of "...collisions in the disk tended to make orbits more circular explains why most planets in our solar system have nearly circular orbits", which seems a very reasonable proposition. I've also come across what looks like a quite exotic answer to this question along totally different lines by the astronomer L. Nottale in a paper entitled SCALE-RELATIVITY, FRACTAL SPACE-TIME AND GRAVITATIONAL STRUCTURES. His work has also been discussed in these forums. I find both the paper and the discussion far above me, though. Can anyone help to straighten me out with the current consensus on this question? Has it been thoroughly worked through by theoreticians? If so, I'd appreciate a web-accessible simple-minded reference to how this was done.