This is a ridicously high payout rate...
Since you are new, people will ask for escrow or upfront payment to make sure that this is no scam.
I could make it lower? We have a certain amount of BTC put aside for marketing and we thought that paying a higher rate would persude people to use us and not use other advertisers.
as for paying up front, what is to say someone wont run away with the BTC?
Well, the money is yours, do what you want. But the more you pay, more spammers will come, the more work you will have to review trough all the posts of all of them. Stunna at his ad campaign saw that he was paying too much because of spammers and now he cut a lot of people from it.
About upfront payment, don't give it to anyone ofc, see their trust in the forum first to make sure that everything will run ok.
But I think that escrow still a better idea.