After an exhausting internet search (2hrs - I love soccer):
Unless these news sites are lying. THE VIDEO IS A FAKE.
I translated both a danish website and a norwegian website and both report nike ad execs and ronaldinho recently admitting the video is fake. As near as I can tell they say there was another person in the video who kicks the ball back to him, and they have simply removed him from the video using greenscreen techniques.
Also note, that this is crazy, but the 3 guys in the background hardly take notice. All of his teamates claim the video is "impossible" and "fake" in press conferences. Zindane Zidan also claims its fake.
While he is insanely talented, the margin of error is less than a centimeter for that ball to bounce back prefectly. Both the cross bar and ball are round. Think of the physics.
Anyways here are the links, dont know if i will link them properly
and
Also, a show on tv appeared where they showed how it was/could be done with a green screen and cameras all around etc etc. Watch the begining of the video when they bring the shoes in. There is a man lying beside the goal who disappears later. What the hell is he doing? anyways check out this forum:
And its pretty much confirmed that it is fake. If it turns out its not fake (i.e. he repeats the stunt) then I retract my statements, I am merely presenting facts and compiling them for you guys. He still has insane skill and deserves to be world footballer of the year.
Also, recall the ads they are running right now of that touchdown catch, jordan missing that shot, all those great sports moments. They were able to edit all the elements of those ones (including the whole crowd in the jordan clip - not celebrating/celebrating) so why not this clip. And the Burger King ad where the King runs in a touchdown. That was all CG (computer graphics).
Conclusion - GREAT PUBLICITY STUNT. Ronaldinho is still one of the best in the world.