There are ways you can use multiple accounts and there are ways you can't. For example one big no-no is using multiple accounts to max bet on a game. Let's say there is a max bet of 1 bitcoin on a game, and you have 10 bitcoins you want to wager, you can't just open 10 accounts and wager 1 bitcoin on all of them. That is not allowed and that will get you banned and moreover you will not only get the wins and all of the bets will be voided but you will also lose that 10 bitcoin you played with as well.