Before the conspiracy theory guys climb in, we use a simple system to select the winners (and have for a while). It can easily be checked, so if you truly believe that the competitions are not fair, I will gladly explain the system to a forum rep, and they can confirm that there is no funny business going on (I do not want to publically show the method as it can be manipulated).
Shouldn't you be using a system which cannot be manipulated at all?
Grats to the winners.