Wow, the poster above is a real jacka$$.
While it is normally a good idea in the 747 to smoothly "fly" the nose onto the ground after landing, some pilots for whatever reason like to hold the nose off occasionally. This is theoretically for "aerodynamic braking," but any text about jet flying will tell you that you should get everything on the ground as soon as possible (smoothly) to take advantage of all available resources (thrust reverse, anti-skid, spoilers, etc.) Many aircraft need to be flown onto the ground (see the 727) and reward a firm touchdown, rather than trying to "hold it off" and grease a landing. With a max landing weight of around 630 thousand pounds, the concern with a classic series 747 is getting it stopped.
Note that in the video only the inboard engines are in reverse. It is possible that one or more reversers were inop, thus the pilot thought s/he could help the landing distance by taking advantage of the aforementioned "aerodynamic braking."
Hope that's helpful, unlike the smarta$$ reply above.