You can land down wind, but you have to be very careful that you don't overshoot the runway. The only time I do a down wind is if I'm dead stick and that is my only option. Figure a 5mph head wind and you are landing at 10MPH ground speed. Air speed of 15mph. Turn it around, and add the wind to the air speed to get ground speed, now at at ground speed of 20mph. The problem is that you judge your landing speed in relation to the ground, You sense you are going to fast and you keep cutting throttle to slow down. To get down to the 10mph ground speed you are used to, your air speed is going to be down to 10mph and that my be enough for a full stall. If a gust hits, you can be in big trouble. Remember that the wind is not a constant, but variable in both direction and speed. You have to have enough air speed and momentum to handle the changes.

I've seen a couple very seasoned flyers drop their plane landing up wind . On one ocasion, the wind was just about steady 15mph straight down the runway. The guy was flying a 3D and it was hovvering into the wind and slowly loosing altitude. He was down to about 10 ft when the wind just quit for a second. He had no momentum and was suddenly at an air speed of zero. He picked up the parts. The same thing can happen with a gust when landing down wind.

Don