The https://www.betcoin.ag/ site is not down and this is not one of those typical scams which you are referring too. I remember betcoin.ag promoted their site through signature campaign a few years back and it was one of the best campaigns. You will always find some complaining because of their own personal bad experiences.
There are giving 100% bonus up to 1 Bitcoin plus 10 free spins but is it only for the new signups ? Whats about the old sincere users of the site ?