When you're handling someone's money, there's an expectation of greater accountability. That is particularly true in a situation like this, beta or no beta, since the owners of coinmarket.io are generating their own profit via their clients' transactions.
Thats the thing.. They are not handling money. Especially Coinmarket that doesn't even exchange into Fiat. Crypto is not money, officially, to anyone outside Crypto. We could be trading dolls, or beach sand. We in this community believe that it stands for what the rest of the world uses as money, but that has been made clear officially by many countries.
Its not money.
Beyond that, exchanges as we know them now have no insurer, no regulation, no governing body, professional group, or even ethical standard. We have the power of general opinion, demand, and some vague notion of community respect for semi-anonymous pseudonyms that run these things.
I have coins on exchanges. I occasionally trade them in for real money, or Fiat as its often termed here. But to pretend that while its out there it has the same kind of security as the systems we have built up over the last centuries for our currency, while they constantly brag about not doing so, is irresponsible.