lately they do have ZrCoin too which isn't released yet. are they doing IOU for this SONM? after zrcoin was listed to hitbtc, the zrcoin team announced that the zrcoin on hitbtc were fake. this SONM from hitbtc must also be fake.
It is possible they're selling something they don't own yet, like a futures contract.
They are selling SNM at 0.25 BTC (https://hitbtc.com/exchange/SNM-to-BTC)
from hitbtc
Quote
Please note that SNM is an IOU for future issued token. Until the token is released withdrawals and deposits are unavailable. Please accept our apologies for the inconvenience.
Avoid buying the IOU tokens at hitBTC because i think they are not even providing any proof that they bought the tokens in crowd-sale (i guess).