From what I've seen reported, several people have assumed that the meteor that streaked across Siberia and exploded was actually a pair of meteors in close formation, which is why there were two smoke trails.
But look carefully at the trails. That knot toward the right could be rising air from the heat released in a particularly large explosion. Besides that, notice anything familiar about the way the smoke trails look, the way they seem symmetric in intensity as well as parallel, not divergent at all? See also
this video of the meteor (careful with the volume at the sonic boom or explosion sound at 00:28!).
747 with engine contrails entrained in trailing vortices
It takes two aspects of a single body for it to make an airflow pattern like that: lift and stability. Stability to make it continuous instead of intermittent, and lift to generate a double-vortex pattern. How does lift make a double vortex?
757 showing trailing vortices via entrained cloud top
Like that.
It's a pretty wild idea that the meteor could have been a stable lifting body shape, on top of the mere fact of the meteor itself! Even wilder and more fantastic (in the literal sense), seeing as how the double trail continues after the knot-like portion of the cloud, is the possibility that the meteor maintained a stable lifting shape through an incredibly huge explosion.
Perhaps it looked like one of our early experiments on the shapes that eventually led to the Space Shuttle:
Or perhaps its stability came from spin, like a discus! As with a skipping stone, spin stabilization can enable many shapes to generate sustained lift.
Or perhaps there was some other dynamic at work. But, going by the shape of the smoke trail, I bet there was lift and stability involved.
In this video, you can see the gigantic lingering fireball from the explosions:
Somewhat relatedly, if you have any moronic friends who go on about "chemtrails," send them to Contrail Science.
Update 10 AM Feb. 17, 2013: Location corrected from Siberia to Chelyabinsk
Update 10 PM Mar. 5, 2013: Reflecting on this post, I now believe that I had the whole phenomenon upside down. In the video, you can clearly see the fireball rising, as of course any hot pocket of air would (in this case an incredibly large and toasty "pocket"). That's effectively that 757 picture turned upside down. The line of hot rising smokey air would split to either side into the parallel vortices that you see. In that case, the meteor would be a non-lifting disintegrating/exploding body of material, per the typical characterization of a meteor. It's like a nuclear bomb's mushroom cloud, in linear form. Perhaps what threw me off was the clear gap between the smoke vortices.