Why the prediction should be email you should publicly post it here or on the facebook so that it will be fair to those who join and participate.

Honestly, what I see here is the way how you promote the website and get it free signals from your audience for free if you allowed someone to send privately in email you can make a fake account and telling that he/she won the game.

Much better all pm or emails are ignore and only public prediction on the comments should be counts as valid prediction. So that we know you are fair.