Thanks for posting that. I have a couple of comments and a few questions.
http://churchofcriticalthinking.org/planetx.html
some good info to read which may help some understand the concept a bit more
So this also implies that this planet is in orbit around the Sun. Are we in consensus then that this theoretical object is in orbit around the Sun?
As I was reading this article, it occurred to me that none of the math makes any sense. There are formulas without any basis ... almost as if the result was driving the formulation of ideas. For example, sexigesimal number systems don't work like that. There's no tens in there. It goes 1, 60, 3600, etc.
There is reference in the article to what is described as a 'pole shift' that occurs every other orbit. It doesn't go into any detail as to what that entail, or how it is physically accomplished.
According to this guy, "[FONT=Arial, Helvetica, sans-serif]
[FONT=Arial, Helvetica, sans-serif]Sumerian and Mayan text both state that Nibiru is clearly visible by day as well as night[/FONT][/FONT]". Now let's assume Nibiru will return in 2012, that means the last time it visited was around 1590 bce (2012-3600) and before that around 5190 bce (-1590-3600). So the first Mayan settlements were around 1000 bce and the Mayan collapse was by around 900 ce (AD). The earliest reference I could find for the Sumerian pre-cuneiform was around 3500 bce and Sumer's renaissance appears to be done by 1700 bce. It looks to me that neither of those cultures were around to witness this astronomical event. I suspect the texts he was referring to reference some other events.
Finally, he references some news articles concerning Planet X in the media. Now, sure, there was an unexplained wobble to Uranus. Unexplained, that is until a couple of smart guys figured it belonged to another planet. Their predictions were within one degree of where Neptune was discovered. Then there was a little more uncertainty and it still didn't get resolved with the discovery of Pluto (or Charon). It wasn't until 1993 when they revised the mass of Neptune due to the flyby of Voyager 2 that the gravitational effect of Neptune on Uranus was completely satisfied.
I'm sorry, but again I'm not finding anything compelliing.