Such position enables better filling of intake channels and reduces the turbulence of air going from snorkel into trumpets. If they would be fixed sideways or similar to his position but deep inside it would cause reduction of intake channel diameter, worse atomisation of fuel and worse mixing with air.
The injectors are very high pressure, and when opened, spray out a very fine mist. The idea is to break down the gas droplets into as small pieces as possible, to give better fuel burn. Being so far from the combustion chamber, this gives the air fuel mixture more time and chance to evenly disperse into a very, very fine homogenous mist before it enters the combustion chamber. Remember, a large droplet of fuel won't burn properly, you want a complete, controlled burn with the gas droplets as small and evenly dispersed as possible.
FIA technical regulation 5.7 Fuel systems
5.7.2 Only one fuel injector per cylinder is permitted which must inject directly into the side or top of the inlet port.
No way, a lot of air is sucked through those trumpets, and all the fuel goes into combustion. Even at an average of 15,000 RPM, the engine sucks in 18,000 liters of air each minute.
The fuel also vapourises which cools everything down, increasing the density of the inlet charge (fuel air mix) and contributes to greater power.
The mist is caused by the pressure drop around the inlet trumpet, rather like that seen over the upper side of a fighter plane wing during a high G turn.
http://video.google.com/videoplay?docid ... 9926133763 very 
