In today's batch of new preprints is:

http://arxiv.org/abs/1204.5187

by Boley, Payne and Ford. Submitted to ApJ.

The paper discusses planet scattering and other matters relevant to
exoplanet systems.

Quotation from abstract:

"...auto-ionization is likely to remain the dominant source of free-
floating planets."

In a relatively short time we have gone from planets in relatively
"permanent" orbits to planets undergoing extensive "migrations" and
planets being ejected ["ionized"] from stellar systems.

Our understanding of stellar scale objects and exoplanet systems is
evolving at a remarkable pace, while the engine of particle physics is
racing in "park".

Personally, I find the directions of this evolution highly
enlightening.

Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity