Sorry for the delay in our return, but we got some GREAT news!!! FINALLY we will be launching some markets on BitcoinTalks!!! 
Stay tuned!
Then this will be one of the great news we have from your end because after months of waiting about this suggestion at least you will give what Bitcointalkers ask you and that is something about the forum.Stay tuned!
But please put in mind some advise from reputable forum members to not step behind the rules or the ethics of the forum.
Bitcointalk community: What do you think would be the best suggestions for markets? So far from famososMuertos we have:
• When will the first user reach 10,000 merits?
• What year will the first user reach 10,000 merits?
• When will user number 4 million register?
• When will the first user reach 10,000 merits?
• What year will the first user reach 10,000 merits?
• When will user number 4 million register?
Whom from theymos or loycev will first reached that awaited 10,000 merits 
I think this is a bad idea: Betting money on predictions that can be influenced by users means it can be cheated. And users can be accused of cheating without even knowing these bets exist. So please, leave me out of this 
The same goes for reaching 4 million Bitcointalk users: spambots can easily create many accounts, even if they can't post because of evil IPs.
hope this at least will give you some good hints what to put in game and what's not.