it is one and only site that accept CLAMS and it should be backed by or related to developer of clamcoin so there are less chances of this to become a scam, i m not saying that it is 100% safe i m just telling it logically that you can trust it as much as you trust other online gambling sites
There are more website using clam as currency, yesterday I played in a website where you could play any casino game and dice with clams and exchange the clams to btc in the same casino.