so u're asking with other words, how can we know when scammer will run ? u cant ...this is not gambling ... its stupidity ...
Sure it is gambling, you are gambling on the site behaving fairly. I think odds can be calculated, but the calculations are very complex and well beyond simple math.
Anyway, any gambling site can be "hacked" at any moment. Many have especially in the altcoin world. Can you be sure none of those weren't the same, that is the operator just ran off with the money?