It depends on your level of friendship online if it's an old friend and you know where he lives or you are both acquaintances, then you can add excitement to the game by playing for money, of course, an escrow is recommended if the amount is huge but if it's pennies then you should honor your words.

I used to play email chess a long time ago, in fact someone on this forum also I met there before I picked up on bitcoin. It is fun, but you always knew when you were playing against someone using computer software, which is impossible to detect just have a lot of suspicion when you try ask them why they make the move and they cannot explain.