Another post on this board has got me really wondering about this stuff about Planet X (Nibiru), etc.

http://www.planetxvideo.com/intro.php

Does anyone have any info?

For starters, I would be concerned about any theory Nancy Lieder supports.  I believe she appears in the video you posted.  I mean, after all, the woman claims she was contacted by a race of aliens, called Zetas (short for Zeta Reticulans, aliens from the star Zeta Reticuli), who implanted a communications device in her brain so they could keep her up to date.  When Hale-Bopp showed up, she claimed  "The Hale-Bopp comet does not exist. It is a fraud, perpetrated by those who would have the teeming masses quiescent until it is too late. Hale-Bopp is nothing more than a distant star, and will draw no closer."  I'm assuming you're all old enough to have actually seen the tail with your own eyes.  Also, she was convinced that this planet was actually supposed to show up in 2003 - so convinced she told all her followers to put down their pets, which they did.

As far as the theory itself goes, it proposes a very large planet that's on its way towards us.  Alright, but if it's going to reach us any time soon, why can't we see it with the naked eye, as we see Jupiter?  The video seems to imply that perhaps we're missing it as comets have been missed, but we're talking about a massive planet, not a comet in this case.  And as far as any of that NASA keeping it hidden trash, they can't blot out the sky.  Amateur astronomers around the globe should be identifying it.

Yes, I'm sure someone here would know more about this than I do, but I've come across two different ideas concerning PlanetX, or Nibiru - 1). that it's actually a planet; 2). that it's actually a brown dwarf.

Brown dwarfs are a "failed stars," larger than a planet, but incapable of sustaining hydrogen fusion.  Their formation leads them to be rather hot, giving off radiation in the infrared red, but very little visible light.  So yes, the primary means of detection for brown dwarfs is via infrared.

But, if this dwarf was preparing to swing by us soon (I believe they're saying 2010), it would be much closer than anything else we're looking at, and I believe the light from the sun would be reflected off of it like other planets.  More importantly, a brown dwarf would have strong gravitational effects on the other planets.  The first video posted mentions ice caps melting on Mars - what we'd really be seeing first would be that the orbits of the planets would be altered.  

If a massively large solar body was about to pass by us in 18 months, it should be visible already.  I don't know how large Nibiru supporters claim it is - let's say it's somewhere around the size of Jupiter.  It takes Jupiter over 11 years to complete it's orbit.  Even when it's at its farthest from us, we can still see it very well.  Pluto takes 248 years...  I would imagine Nibiru would have to be closer than Jupiter, or at least, as close as Pluto, and in either case, at that range, we should be able to see it, as we can see those planets.

As far as blotting out the sun for the entire planet, what I know of eclipses makes that seem impossible.  But I'm not an astrophysicist.      

Just for the sake of argument, is it not possible that the visibility would be minimal if it were approaching from a vantage point where we are more or less blind?  Just as there are stars that we never see, we do not see more than half of the sky on any given night.  Even then, the view from the northern hemisphere is not the same as it is from the southern.

IMO, we are going to get incomprehensibly rocked, Nibiru or no Nibiru.  We have accrued an incalculable debt that is about to come due.