wouldn't the biggest risk be the site owner (not just JD, any other such sites) running away with the money? ( or is it technically hard to do? )
no it's not hard to do and it did happen before , I remember DaDice which used also to take investments and there were spending a lot on signature campaigns and faucet then they scammed the money
the thing about Dadice that they weren't even one year old , while the majority of the sites here are well established and trusted
so it's a matter of trust at the end , but there is always a possibility for the owners to run away or make some claims like they were hacked
But I never know anything about JustDice is going to scam everyone, if I not mistake there is really huge payout there when they are still on top using btc as their main coin. Buy after many of big whale start to win a lot of coin they are suddenly change to clams to play and the site is still ongoing. There is only lack of informations on what a old site should be to maintain their players to play there