Directbet, just a thought. Maybe you want to limit at least to members or full members and above. Look at all the newbies and members right when you announced the new contest. Very easy on the soccer front to cover all the scores and can be done with alt accounts. Things like that have happened many times in the past on these forums.
We prefer to keep this promotion open to everyone, but check out our Basketball prediction game where you can pick a score that was already picked by someone else. Next prize there is 110 mBTC !
Also, we will soon introduce another contest where you will not be limited to unpicked scores.