It's not necessarily unfair if a member that contributes a lot to the forum thus earning enough bucks to spend max entries each week and wins twice or 10 times before someone wins once.
The only thing that would make it unfair would be for Anker to award everyone a prize (currently 694,107 users) before you could win a second prize but that would defeat the whole purpose of contributing and awarding bucks.
Not everyone can or should win or it would not be a draw.
DRAW "an act of selecting names randomly, typically by extracting them from a bag or other container"
I do feel somewhat guilty winning more than once when you have not and that's why I don't play poker...be patient