Bitshares is a ground-breaking "high performance, decentralized exchange", which .. allowed for the easy listing of short-lived relatively-schlockey coins/tokens, as well as the more solid and well known ones. The point is, it completely eliminates the potential for a Cryptsy, a Bitfinex, a Mt.Gox and so on, as each user controls their own keys - it is basically a wallet and a means of exchange, without anyone at the center able to pull the plug, or otherwise mess with deposits.

STEEM is not one of those tokens and the only exchange that is supported is between SBD and STEEM, which I believe I have heard happy mention (or did come to me in dreams) will soon no longer be the case, as STEEM Backed Dollars will be properly eliminated.