re: Eris and Dysnomia,
Maybe, just maybe Pluto just could not come in any further because of Neptune's faster rotation during the early history of our solar system. Then, Brown would be right.
Ok, that was an afterthought. :)
The quotes in my post above are from: http://www.astronomy.com/asy/default.aspx?c=a&id=4474
Best.
* We still have July of 2015 to look forward to when New Horizons whizzes by the Pluto and Charon... Eris and Dysnomia. Who knows what else New Horizons may find.