"We have retained the generous upper mass limit of 24 Jupiter masses in our definition of a “planet”, for the same reasons as in the Catalog: at the moment, any mass limit is arbitrary and will serve little practical function both because of the sin i ambiguity in radial velocity masses and because of the lack of physical motivation.
The 13 Jupiter-mass distinction by the IAU Working Group is physically unmotivated for planets with rocky cores, and observationally problematic due to the sin i ambiguity. A useful theoretical and rhetorical distinction is to segregate brown dwarfs from planets by their formation mechanism, but such a distinction is of little utility observationally."
^ abThe Exoplanet Orbit Database, Jason T Wright, Onsi Fakhouri, Geoffrey W. Marcy, Eunkyu Han, Ying Feng, John Asher Johnson, Andrew W. Howard, Jeff A. Valenti, Jay Anderson, Nikolai Piskunov
^Catalog of Nearby Exoplanets, R. P. Butler, J. T. Wright, G. W. Marcy, D. A Fischer, S. S. Vogt, C. G. Tinney, H. R. A. Jones, B. D. Carter, J. A. Johnson, C. McCarthy, A. J. Penny, The Astrophysical Journal, Volume 646, Number 1, 2006