ndnhc's advices.
![Cool](https://bitcointalk.org/Smileys/default/cool.gif)
1. Use an escrow.
Details:
Get an escrow, transfer funds to be held with him as long as it is running. Funds should be a reasonable amount.
2. Lower the fee. A 5% is good enough. The lower the better
3. Make the game provably fair.
Details: You can hash the url of the winning satoshibox link or the number or both with random characters to avoid players brute-forcing it, using a one-way hashing function like SHA256, publish the hash before the game. When the winner is announced you will have to publish the message you hashed.
Illustration:
Your winning box is 102
http://satoshibox.com/55eae63WRFQWFe12fb6b456cYou hash 102:http://satoshibox.com/55eae63WRFQWFe12fb6b456c:randomtextndnhc using SHA256.
You get
e2ce2bf3a310658c603b92202e2819d2a319cc674bcd97d14b95c54bf530ba0f which you publish before the game, and the initial message after the game is over and the winner is declared.
Thanks
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
That would be 0.025
BTC.
Not intended to be taken seriously.