It's right here, captured by myself.
 http://www.youtube.com/watch?v=_Hf-CD6L6dM
 
This is a pretty bad glitch that needs to be patched pretty urgently.

Happened after skydiving. Then I skydived off a cliff and then glitch stopped

LOL awesome, you can now enter houses and buildings haha!  Maybe you typed IDCLIP cheat code ;)
 
Seriously, that has not happened to me yet so far in my playtime with Just Cause 2.  The one glitch that I noticed is in some of the buildings around the Panau Residential District I think, and there are some areas on rooftops that Rico just suddenly falls in like quicksand, so half his body passed through the concrete.  Then when he walks on top of it, blood splatters around his feet.  Weird, maybe I should record it next time. :)

HAX

Have played over 20 hours. Never saw it.

Haven't experienced it.  

Just Cause 2 has no glitches - those are features. :)

Open-world games will always beg for these things to happen. I'm currently also playing inFAMOUS and I came across a glitch that made me fall through the ground whenever my feet hits the streets. Obstacles (signs, towers, etc.) were fine, but rooftops and streets acted like quicksand. Luckily, falling through and starting over fixed things, which is usually the case with these issues.
 
Glitches provided some of my favorite moments in the GTA series.

That would be pretty handy if you are able to find all the crates with it easily.

there are a few of these glitches, came across one today, a faction mission where i had to kill a mercenary trainer and i had to go to a military base but i had to go over a bridge, so i took a car a started driving towards the bridge suddenly i just went through the bridge fell down and crashed the car in the river below, and when i did get over to the other side the military guys just shot through the buildings i died before i could shoot back :D the other one i saw was a military airbase on a very high mountain, a big part of it was normal but a small part was a bit higher up and it was fully walk through :D
 
Allen :p

Also known as physics lag.  The building models are loaded separately from their hitboxes to allow for diffferent scales of LoD (level of detail) streaming and at some point these two go out of synch with eachother and while the buildings loaded their hitboxes didn't or were offset (most probably below the ground).